The first thing that strikes you is the panorama gaping wide and westward, out over Richmond Park and the Thames to Ham House, Eel Pie Island, Pope’s Grotto, Kneller Hall and, faintly crowning the horizon, Windsor Castle. That the telescope set in the middle of the clearing points east seems incongruous. The view that way must surely be obscured by the holly trees which enclose the summit of King Henry’s Mound and, beyond, by Sidmouth Wood, as dense a copse as any in this corner of the royal park.

The arbour set in that section of the foliage, similarly, feels like an oddity, but all the compass-style arrows carved into the floor of the viewpoint demand you point the glass in that direction. So you comply and, once the eye has adjusted, the cutting does leap out at you. A thin avenue has been pruned from the branches of the thicket, extending from The Way gates across Queen’s Road.

And there, nestled in a keyhole of light with its dome resplendent in the sunshine, lies St Paul’s Cathedral.

The landmark stands on Ludgate Hill a distant 10 miles away, slap bang in the heart of the bustling City, a world apart from the birdsong and tranquillity of the gardens. But, from here, the view out to Sir Christopher Wren’s masterpiece is uninterrupted. Improbably clear. Beautifully precise. Immaculately framed.

It takes a while to tear the gaze from the familiar drum colonnade and rotunda, a vision of shimmering white. There is the inevitable muttered curse that the backdrop has been infiltrated by the hulk of a high-rise, recently constructed in Stratford even further to the east having exploited a loophole, since closed, in governmental planning permissions. But, for this observer, it is the foreground that is of particular interest.

There, visible just above the tree line, is the triangular truss jutting out from the roof of the west stand of Stamford Bridge. At 49.19 metres, the angle of the pylon marks the highest point of the current stadium and does not impede, in any way, the view across to St Paul’s.

Yet, in their sales pitches to Raine Group in New York, each of Chelsea’s prospective new owners has pledged to redevelop the stadium. They have been enticed by the prospect of increasing annual match-day revenues from £70 million to closer to £200 million by finding another 20,000 seats on a desperately tight site. It has also been made clear that they must demonstrate a will to succeed in one of the few areas where Roman Abramovich came up short, by enlarging and modernising the club’s home of 117 years. Instigating that revamp will constitute a demonstration of long-term ambition.

Chelsea’s home ground is hemmed in by a railway line and a cemetery, the Fulham Road and private residences. Instinct might suggest the obvious architectural solution would be to “build up”, but that would not be simple given the restrictions on the plot, not least rights to their neighbours. Besides, in what some might consider a quirk of local law and others cherish as a key safeguard to preserve something utterly unique, development is also limited by that sightline from that knoll in Richmond Park a little over five miles away.

This is the story of why the glorious view from a Bronze Age barrow, a small mound bearing a name that is shrouded in romantic myth, is so cherished and will effectively thwart any of Chelsea’s suitors from looking to the heavens when they seek to increase the capacity of Stamford Bridge.

First, a history lesson. Actually, let’s begin with what is probably the stuff of legend.

It was the English historical writer and poet Agnes Strickland, in her 12-volume tome Lives of the Queens of England, scripted between 1840 and 1848, who expressed in print an account handed down orally from father to son by the various parkkeepers in Richmond, south-west London, over the previous three centuries.

Strickland’s wonderfully vivid inside story, complete with first-hand quotes apparently direct from the scene, went that, on the morning of May 19, 1536, Henry VIII “clad for the chase with his huntsmen and hounds around him, was standing breathless on a mound in Richmond Park, awaiting the signal gun from the Tower (of London) which was to announce that the sword had fallen on the neck of his once entirely loved Anne Boleyn”.

Anne had given birth to the future Queen Elizabeth I but, having failed to provide the King with a male heir and with Henry now seeking to marry Lady Jane Seymour, had been arrested and sent to the Tower. The trumped-up charges against her included adultery, incest and plotting to kill the king. She was convicted of high treason on 15 May. The executioner’s sword fell four days later.

“At last, when the bright sun rose high towards the meridian, the sullen sound of the death gun boomed along the winding of the Thames,” continued Strickland. “Henry started with ferocious joy. ‘Ha! Ha!’, he cried with satisfaction. ‘The deed is done! Uncouple the hounds and away!’.”

Seymour was apparently waiting in the Richmond house of Sir George and Lady Carew for news of her predecessor’s grim fate to free the king to marry her, which he duly did eight days later. The mound from which Henry descended in such delight has borne his name ever since.

It is a wonderfully sinister and evocative Tudor tale. The rumble of the canon has been replaced by a black flag, which must have been quite some size given it is 11 miles to the Tower, and even a firework in some accounts. The only slight problem is that it is probably apocryphal. Rather, there is strong historical evidence that the king spent the evening of his wife’s execution at a knees-up at Wolfe Hall in Wiltshire, some 60 miles from Richmond — a day’s ride at best by horse.

But why let an inconvenient truth interfere with a fine story?

Now for reality. The steep-sided mound, situated on the highest part of Richmond Hill among the north-western reaches of the largest of the royal parks, is thought to be a barrow dating from between 2400 and 1500 BC, a rarity in Greater London today. The naturalist Edward Jesse, writing in 1835, described how “it has been opened and a considerable deposit of ashes found in the centre of it”, although the remains were not necessarily of human origin.

The Royal Commission on the Historical Monuments of England carried out more recent archaeological survey work on the site in 1995 and suggested there was evidence of prehistoric origin. There is another probable burial mound, dating further back to the early and middle Neolithic periods, some 600 metres to the east on lower ground, an area once known as Oliver’s Mound, that was destroyed by gravel digging in 1834.

It has been suggested by archaeologists that the vantage point, at 57.4 metres above ordnance datum, could once have been a castle mound, albeit, at around 36 metres in diameter across its flattened top, it is rather small for a motte. It certainly had other uses in the centuries which followed. The area has a long tradition of hunting, dating back to the 14th century, when it formed part of the Manor of Sheen. A royal palace was built nearby and became popular with Henry VII, who named the estate “Richmond” after his earldom in Yorkshire, with both Henry VIII and Elizabeth I known to have hunted there.

The new park was only enclosed during the reign of Charles I (1625-49) and, on Elias Allen’s map drawn in 1637, the mound is marked as the “Kings Standinge”. It was effectively a convenient perch from which a monarch partaking in a spot of deer hunting could enjoy clear views over the surrounding land, with game driven up the hill into his path to be shot.

Evidence of the celebration of the view east, with its implications for modern-day planning permissions, emerges in maps and illustrations from the early 18th century.

St Paul’s Cathedral, gutted in the Great Fire of 1666, was rebuilt to a modern design schemed by Sir Christopher Wren and declared officially complete by parliament on Christmas Day, 1711. At a height of 111.6 metres, it dominated the London skyline and was clearly surveyed from the distant hill that was, for a while, referred to as King Henry VII’s Mount and, later, Henry VIII’s Mount. Some confusion existed as to which Henry had claimed the standing as his own.

An engraving of nearby Petersham Lodge by Kip from 1710 — the summit is topped by four trees — and John Rocque’s map of London, 1741-5, both show an avenue leading north east on the vista line to St Paul’s, the latter in the direction of Oliver’s Mound. That view might have been threatened in the early 19th century when Sidmouth Wood was laid out. Yet a landscaped “ride”, or gap, “was cut through it, which opens a fine view of London and St Paul’s” according to Jesse.

The mound, having already been transformed from barrow to hunting vantage point, was now a garden feature within the grounds of Pembroke Lodge. “This is very much a manufactured view,” says Max Lankester, a former secretary of the Friends of Richmond Park and now a vice-president of the charity. “That keyhole has been cut through the shrubbery around the perimeter of the mound. The avenue through Sidmouth Wood has been specifically enabled and created to highlight this vista.”

For more than 100 years, that unlikely corridor to St Paul’s was maintained and enjoyed, either from the summerhouse up on the mound or the landscaped route up to its brow. And then, probably during the Second World War with so many of the grounds’ gardeners having been called up to fight, it was forgotten.

The holly choked the arbour up on the mound. The avenue across the parkland became overgrown. The ride through Sidmouth Wood was thickened by overhanging branches. The thoroughfare was cluttered with rhododendrons and neglected.

By the time Chelsea set about rebuilding the East Stand as a three-tiered cantilever to 37.82 metres at Stamford Bridge in the mid-1970s, a move that would near bankrupt the club, there was no vista to threaten.

The viewing corridor passes through Sidmouth Wood, over lower ground within Richmond Park and across the wall close to Adam’s Pond. It skims the top of Stamford Bridge and clears Sloane Square, Belgravia, the Wellington Barracks, part of St James’ Park, Downing Street and the Ministry of Defence building on Whitehall beyond, then cuts over Hungerford and Waterloo bridges to St Paul’s.

At its full extension, it affects 11 London boroughs, from Richmond-upon-Thames at source to Newham, lost in the cathedral’s backdrop. In such a sprawl of a city, it is vaguely remarkable that it has remained unobscured given legally protected status was only achieved relatively recently.

It took a local resident called James Batten, studying Rocque’s 18th-century map in early 1976, to piece together that the lost avenue marked veering north east must once have had a purpose. In his student days, Batten had peered through the keyhole in Piranesi’s doorway into the Gardens of the Knights of Malta on Rome’s Aventine Hill and spied the framed silhouette of St Peter’s three miles away across the Tiber. Here, buried beneath the foliage and stretching out much further to 10 miles, was London’s equivalent.

He worked with the superintendent of the park at the time, Mike Fitt, to hack through the shrubbery and uncover the trellis on the summit of the hillock. The trees in Sidmouth Wood were cut back to open up the corridor and restore the sightline to the City.

The vista’s existence, presented to Greater London Council, played a part in thwarting British Rail’s plans to redevelop Liverpool Street station, which would have blighted the backdrop to the drum and dome of the cathedral when considered from King Henry’s Mound. A period of intense campaigning ensued, aimed at having the linear view safeguarded in law.

For context, the capital’s various boroughs were already crisscrossed with similar corridors — albeit none quite as long — aimed at guarding iconic views. Those gazing directly at St Paul’s include the views extending from Primrose Hill and Alexandra Palace, from Greenwich Park and the centre of the bridge over the Serpentine, or from Parliament Hill and the gazebo at Kenwood House.

“There is an architectural significance to St Paul’s, clearly, but the existence of these corridors extends beyond that to the building’s meaning for London and, indeed, the nation,” says Mike Dunn of Historic England, formerly English Heritage, the UK’s statutory adviser on heritage since its foundation in 1983. “It is a symbol. What it represents is important. These corridors are designed to ensure it can be seen from various vantage points across the capital, and that nothing should encroach on the silhouette of the dome.”

As far back as 1938, the Dean and Chapter of St Paul’s Cathedral, together with the Corporation of London, had struck a gentleman’s agreement with developers that restrictions to building elevations would be applied to maintain those sight-lines of the dome. There had been concern that the relaxation of height restrictions — new buildings had been limited to four storeys since 1667, a year after the Great Fire, but extended in 1930 to 30.48 metres, the maximum length of the London Fire Brigade’s ladders at the time — might threaten views of the cathedral.

That agreement, known as St Paul’s Heights, only became legal statute in building guidance plans from the 1980s onwards to reflect that, although no longer the tallest building in London, St Paul’s Cathedral’s symbolic status should still dictate the height, location and even design of other buildings through the City and central London.

But it was only in 1991 that Regional Planning Guidance for London and the Secretary of State for the Environment listed “the strategic view of St Paul’s from King Henry’s Mound in Richmond Park and its viewing corridor” among 34 strategic views of London and one of 10 benefiting from protected status as they were directed upon St Paul’s, the Tower or the Palace of Westminster. The scope of development to the fore of the cathedral, as well as to either side and immediately behind, was duly limited.

“That it is visible from 10 miles away, a focal point even from Richmond dominating the townscape with nothing encroaching on the silhouette of the dome, even from that distance, is remarkable,” adds Dunn. “The mound has been a special place for thousands of years. The specific view out across London has been cherished for at least 300 years. That is why that particular corridor merits the protection that is still placed on it today.”

Successive mayors have tweaked the modern-day London Plan, which pinpoints the viewing corridors to be protected by the Greater London Authority (GLA). The number of strategic views incorporated into the London View Management Framework (LVMF), the GLA’s guidance document on protected vistas, was reduced by the then-mayor, Ken Livingstone, from 34 to 26 in 2007 with the viewing corridors also narrowed. The width of the protected view from Richmond Park was effectively halved, allowing developers to secure planning permission to build around Victoria station.

The resultant construction would not have been permitted under previous restrictions. It is now very visible in the bottom right of the keyhole view from King Henry’s Mound.

Boris Johnson, elected mayor in May 2008 and in office at City Hall for eight years, flip-flopped the other way and restored the width of the channels while increasing their number to 27, 13 of which to be deemed protected.

“For centuries, London has been home to some of the world’s greatest buildings and urban spaces,” wrote the mayor in the foreword to his revised LVMF guidance. “We are privileged to enjoy this architectural history as we go about our daily lives. When we cross one of London’s bridges, walk along the South Bank, or visit one of the viewpoints above the city, such as Parliament Hill, Primrose Hill or Greenwich, we are reminded of London’s history and beauty, and why we love living here.”

Not that the LVMF has entirely safeguarded the vistas it aims to protect. The guidelines extended by Johnson stated that any development in the background of St Paul’s should be “subordinate to the cathedral and that the clear sky background profile of the upper part of the dome remains”. Even so, that was not enough to prevent the construction of the 42-storey Manhattan Loft Gardens skyscraper in Newham, an outlying borough that had been considered too far away to warrant being listed in the original LVMF plan.

Maps of the protected view indicated the background area to be preserved beyond St Paul’s was only 1.86 miles. The tower was 4.35 miles beyond. The development received planning permission in 2011 after the application was referred to the GLA by the Olympic Delivery Authority. By the time the block was springing up next to Stratford station to dwarf the cathedral when viewed from Richmond Park 15 miles away to the west, the legal window to challenge the permission had gone.

The current mayor, Sadiq Khan, did extend the background areas of the 13 protected vistas in November 2018 to the edge of Greater London, closing that loophole. But, by then, the Manhattan Loft development was up. Peer through the telescope on King Henry’s Mound now and it hangs ominously on the shoulder of St Paul’s.

The silhouette of the dome is not quite as pristine as it once was.

That is a reminder that the aspect, viewed through such a small channel from so far away, is fragile. “When a view like this has gone, cut out by high-rise buildings or developments, it has basically gone forever,” says Lankester. “Once you’ve lost it, you’ll never get it back.”

The mayor and Historic England have to be consulted whenever new buildings are proposed that affect any of London’s designated corridors. Stamford Bridge would presumably fall into that category.

The lavish scheme drawn up by the Swiss architectural firm Herzog and De Meuron to redevelop the ground, granted planning by Hammersmith and Fulham Council in early 2017 and City Hall two months later, had considered various options and ultimately determined to lower the pitch. The stadium would only have risen to 46.12 metres, less than the current arena’s tallest point, but it was generally accepted that digging down would add significantly to the cost of the project.

All three of the consortia now waiting on Raine Group’s call will be aware of the intricacies of those plans, which were put on ice back in 2018. They will be familiar with the particular quirks of the site they would inherit. Those leading the Ricketts bid, who withdrew their interest on Friday, had indicated Eric Nordness, who had led the family’s $1 billion redevelopment of Wrigley Field, home of the Chicago Cubs, would have overseen work on Stamford Bridge. He told The Athletic earlier this month that he had already been working on “multiple ideas” with the architecture firm, Populous.

The three remaining bidders have not been quite so open with their plans, but they will have commenced their own enquiries as to what can be achieved on such an awkward plot.

Some might have raised an eyebrow at the reality that those restrictions hampering a rebuild include the view from a hill in leafy Richmond, a world away from the hustle and bustle of the Fulham Road. “But Richmond Park and St Paul’s Cathedral are national landmarks — they are iconic,” adds Lankester. “The park is a National Nature Reserve, one of its many environmental tags. At the last count, undertaken a few years ago pre-COVID 19, it was attracting more than five million people each year on top of those driving through the park. It’s a national attribute.

“Not all of those visitors will make the walk up to King Henry’s Mound to take in the view, but plenty do. And you invariably hear those that do exclaim in surprise that, from a vantage point which feels more enveloped in open countryside, full of plantations and open grassland, they find themselves looking across to the heart of the City of London. That contrast adds to the mystique of the view.

“It just feels so improbable. It will always be precious.”