A SECRET garden has lain undisturbed for almost 300 years under the famous lake at Stourhead, according to a three-year study by the son of the estate's former historian.

Tim Woodbridge has uncovered evidence of a grand and 18th-century garden buried, mostly intact, below the Great Lake at Stourhead.

It is believed to cover at least 200 metres – half the size of the current lake – and includes the foundations of two smaller lakes, a Chinese bridge, an ornamental pool and canal, and the remains of a giant sentinel oak tree, all preserved in silt.

The elegantly landscaped park – created by the head of one of the country’s richest banking families – has been lost to history since 1755. And the cost on unearthing it means it is unlikely to ever see the light of day.

Evidence indicates that its heartbroken owner, Henry Hoare II, destroyed his own legacy by flooding the entire area after the sudden death of his son and heir, Henry III.

The masterpiece he created now sits entombed under approximately 30ft of mud, silt and fresh water below the estate’s Great Lake at its deepest point.

Until now, historians thought the picture postcard lake – which draws countless tourists with its serene setting and iconic Pantheon - was Hoare’s proudest achievement.

The existence of an earlier garden and the tragic story behind its disappearance is revealed in The Choice, written by the son of Stourhead’s master historian Kenneth Woodbridge.

“It’s my view that Henry Hoare’s original garden was very different from the one we see today,” Mr Woodbridge, who lives in Rickmansworth, said.

“It would have been a real tour de force - a beautiful example of neoclassical design that was meant for his son and heir, Henry.”

Woodbridge estimates that the original garden would have cost at least £5,000 to create – a fortune at the time.

Stourhead Manor was bought in 1717 by Henry Hoare I who replaced it with the Palladian mansion still admired today.

But it was his son, Henry Hoare II, who set about turning Stourhead into an Arcadian paradise at the height of neoclassicism in the middle of the 18th-Century.

Hoare, also known as Henry the Magnificent for his generous patronage of the arts, created the monuments and structures at Stourhead - including the iconic Pantheon and Temple of Flora - in his obsessive pursuit to create a dynasty and memorial for his wife, Susan, who died in 1743, and a legacy for his son and only surviving heir, Henry Hoare III.

He spared no expense and hired the celebrated English architect Henry Flitcroft and the sculptor John Michael Rysbrack to bring his ideas to life.

Flitcroft and a team of around 50 labourers are believed to have spent five years, from 1744 to 1749, building Hoare’s dream.

Hoare, a banker and the heir to his family’s fortune, later described the result as “…the fruits of industry and application to business that shows what great things may be done by it”.

Until now the Great Lake at Stourhead, built in 1755, was believed to have been Hoare’s first and only choice as the garden’s centrepiece – a focal point that would create a mirror for the magnificent monuments and temples.

But Mr Woodbridge’s study suggests a very different version of events.

His conclusions build upon the painstaking research of his late father, Kenneth, who spent 10 years trawling through Hoare’s personal letters, bank ledger entries and thousands of other key documents.

His 1970 book, Landscape and Antiquity, is still considered the final word on Stourhead’s garden and was described by The Daily Telegraph at the time as “a work of monumental scholarship”.

The evidence suggests that the Great Lake was, in fact, made to “obliterate” Hoare’s tour de force following his son Henry’s premature death in 1752, aged just 22.

Woodbridge believes that after Henry’s death, Hoare – his spirit broken – found the garden he had made “more pain than pleasure” and flooded it, although almost all the monuments and temples remain.

Hoare’s lost garden, described by Mr Woodbridge as a “hidden gem” of significant historical importance, has been underwater and out of sight since 1755.

Mr Woodbridge’s research suggests that the original garden would have featured two smaller lakes to the north and south, with a Chinese bridge crossing the former, a Grand Canal leading to the Temple of Flora to the east, and an ornamental pool on the west side in front of a grotto that still stands today.

The remains of the sentinel oak, plus the foundations for the original lakes, ornamental pool and Chinese bridge, were detected during an underwater survey in 2005.

Ironically, the flooding of the lake has preserved the remains, which lie under many feet of a very fine silt.

Mr Woodbridge, 71, said the cost of digging up the Great Lake makes it unlikely that the original garden would ever be uncovered.

He added: “Hoare set out to create a lasting legacy for Susan and then for Henry. His lost garden represented the first steps of an artist trying to find himself.

“However, his drive to express his innermost feeling at the loss of his son led him to create a masterpiece, the current garden, which resonates with us today because it speaks to us at a deeper level than if it was simply a piece of good horticultural design.”

Hoare died in 1785 and the 2,650-acre estate, located at the source of the River Stour in Mere, was passed on to his grandson and only remaining heir, Sir Richard Colt Hoare.

It was acquired by the National Trust in 1946 and the Great Lake has become one of its most photographed vistas, understood to attract more than 400,000 visitors per year.

For more information visit Tim Woodbridge’s website, www.stourheadthechoice.com.