£7m to end the torment of a tycoon

Set amid the rolling hills and picturesque woodlands of Northamptonshire, the Manor Farm estate at Brampton Ash is often regarded by many keen shots as one of the finest places in Britain to shoot game. The valleys surrounding the estate's farm houses and bungalows have long echoed to gunfire triggered by many of the country's influential elite, including Winston Churchill, Lord Heseltine and Sir Richard Branson.

But for David Ross, the multimillionaire co-founder of Carphone Warehouse and the 1,500-acre estate's owner, Manor Farm is too painful to keep.

Despite its picture-perfect appearance the immaculately kept grounds are a reminder of inconsolable loss for Mr Ross and his family. Two years ago the tycoon's stepsister was murdered, along with her new boyfriend, by her estranged husband, who entered their bungalow on the estate and stabbed them to death.

Now the grounds and the farm buildings have been put on the market at a price tag – despite current market conditions – twice what Ross paid when he bought it six years ago.

Until the mid-1980s, Manor Farm was one of the many landed properties in the Northampton area owned by the Princess of Wales's family, the Spencers. Mr Ross acquired the property in 2002 for £3m and turned it into one of Britain's most plentiful shoots – renowned for bags of up to 1,000 a day. But now the estate, which includes more than 1,000 acres of arable land, is on the market for £7.75m.

His stepsister Fiona Marshall was just 41 when her estranged husband Alex Marshall crept into the bungalow she was sharing with her new boyfriend Richard Flippance two years ago intent on murder. During the trial at Birmingham Crown Court last year the court heard how Mrs Marshall and Mr Flippance were spending their very first night together in the bungalow where she had lived since her step-brother acquired the property.

In the month leading up to the murder on 2 April 2006, Alex Marshall had managed to hack into his wife's email and had been carefully monitoring her blossoming romance with her new lover, whom she had met on a dating website.

When police arrived at Manor Farm the next day, they found the charred remains of the two victims amid the bungalow, which had been burnt to the ground. Mrs Marshall was later found to have died from eight stab wounds and Mr Flippance was stabbed three times.

Police were able to link Marshall to the killings after DNA from Mr Flippance was found in the footwell of Marshall's car. When police arrested him, Marshall was found to have singed hair and eyebrows and burns on the tip of his nose.

Sentencing him to a minimum of 30 years in prison in April 2007, Mrs Justice Rafferty reminded him of all the lives that his murders had blighted.

Among those is clearly that of Mr Ross, hence the sale. A prominent Tory donor, Mr Ross is thought to be worth at least £873m after setting up the Carphone Warehouse with his old schoolfriend Charles Dunstone. He often holds fundraisers for the Conservatives on his estates and is known to count many prominent Tories as friends. Earlier this year the Mayor of London Boris Johnson appointed Mr Ross to help with the 2012 London Olympics.

If Manor Farm is sold, Mr Ross will still be in possession of a number of other shooting properties across the country including the 2,000-acre Nevill Holt estate, six miles from Brampton Ash. A spokesman for Fisher German, the agents selling the estate, said yesterday: "We are asking for offers in excess of £7.75m, which reflects the current agricultural land price of about £6,000 per acre."