DETECTIVE stories set in Georgian mansions tend to end badly for at least one of the occupants.

Luckily for these homeowners, unlocking the secrets of their Hampshire estate has been rather more rewarding.

Matthew Hill has spent the last 10 years leafing through wills, letters and deeds to trace the history of Fir Hill, his grade II listed home in Droxford.

On Bank Holiday Monday he and wife Georgy Evans are marking the end of the mammoth project, chronicled in an online treasure trove mapping the estate's 250-year history, by opening its sprawling gardens to the public.

Fir Hill has passed from aristocrats to priests and Mayors to the 'Meon Valley Mafia': senior ex-servicemen occupying many of the area's larger houses.

The mansion's remarkable story, told in parts through engravings found during refurbishment, is littered with appearances by those who ruled Hampshire, Britain and, through crown and empire, large parts of the globe.

Work to build a new home on Fir Hill had begun by 1765, according to an etching of the front elevation recently uncovered in plasterwork.

It was owned in the mid-to-late 18th century by Nicholas Purdue Smith, a Winchester wine trader, three-time Mayor and government agent who took the Army to task over its poor treatment of prisoners of war in the city. Handling 3,500 French prisoners at King's House, on what is now Peninsula Barracks, Smith clashed with military chiefs over the welfare of his charges as epidemics gripped the cells.

Following the death of Mr Smith and his widow, Jenny, the estate was advertised in the London Gazette and Hampshire Chronicle. It offered more than 450 acres of "beautifully varied" pleasure grounds and gardens - yours for £350 a year, or around £540,000 in today's money.

The estate was bought in 1797 by Captain Charles Powell Hamilton, the first of several navymen to make Droxford his home. On more than one occasion he welcomed his first cousin, Lord Nelson, to Fir Hill.

Nelson is thought to have been on his way to Portsmouth when he visited in the early 19th century, as Droxford was a key stopping point on the old road from London to the port at the time. A letter from a fellow guest expresses bemusement that this towering figure chose to stay in Fir Hill's smallest bedroom.

The estate was leased to various aristocrats in the first half the 19th century before its next great owner took the reins.

Tom Smith was a larger-than-life fox hunting master who won national renown in the decades of fashionable hunting. He led the famous Hambledon Hunt, which Britain's well-to-do paid up to £4,000 a year (£5.5 million) to join.

Smith also left his mark on the mansion, adding a new south wing and carriage house. As High Sheriff of Hampshire in 1858, he is thought to have built a temporary jail to hold people awaiting trial or charge.

They may then have been sent the village's police station or magistrate's court, built in that year to deal with offences not serious enough to be sent to the Western Circuit.

"We generally see ourselves as part of a chain of changes and renovations," says Ms Evans, an intellectual property lawyer.

"The more we learnt about the house in the 19th century, we realised it has been evolving all along."

In 1950, Princess Margaret visited Fir Hill to mark the 150th anniversary season of the Hambledon Hunt. Joining the ride herself, her royal highness was a guest of its owner at the time, Lieutenant Colonel John Hulbert, part of the military family which owned the estate from 1929 to 1954.

Left in a state of relative disrepair amid rations on building materials, Fir Hill was finally modernised in the 1960s by Colonel Alastair Down, a highly decorated Second World War soldier and oil magnate.

This work was continued by Mr Hill, a lawyer who retired to England after working as counsel for videogames giant Nintendo.

He set about restoring the estate as closely as possible to what was there in Georgian times, working in phases to uncover the building's history as he went.

The extensive renovation made a romantic backdrop when he began courting Ms Evans, he says, because a lack of electricity meant they had to live by candlelight.

On Bank Holiday Monday the pair will open Fir Hill's resplendent gardens for the first time in 20 years.

"We're opening it for the benefit of Droxford Church, St Mary and All Saints, which desperately needs funds for restoration," Mr Hill said. "The gardens haven't been opened since 1995 and we've spent a lot of time and effort trying to restore them over the last few years."

That church, like so much of Hampshire, is woven into the story of this grand Georgian estate. Besides being the site of the Hill-Evans marriage in 2012, St Mary and All Saints is where many of Fir Hill's esteemed owners are laid to rest.

A full history of Fir Hill and details of the open garden day can be found online at firhilldroxford.com.