The Wolverhampton brother of murder in the mansion killer Christopher Foster has called in a private detective to investigate the case, it emerged today.

The move comes as plans are finalised to knock down the remains of Osbaston House, set alight by the failed businessman who also shot dead his wife Jill, aged 49, and daughter Kirstie, 15, before committing suicide.

The family have asked for permission to bury rubble they believe contains some of the remains of the tragic schoolgirl during a short religious ceremony in a wood in the 16-acre grounds but have turned down the offer of a permanent memorial garden.

They want police to hand over a laptop 50-year-old Foster bought three days before the bloodbath which they hope may hold important information about the pressures he faced immediately before the killings at the house in Maesbrook, near Oswestry.

His brother Andrew, a 46-year-old sales manager and father-of-three from Castlecroft, Wolverhampton said: “There are still a lot of things that do not add up and we owe it to Jill and Kirstie to get the truth.

“We cannot draw a line under these dreadful events and move on with the rest of our lives until we have done everything we can to tie up the loose ends.

“We have recruited the private investigator on the advice of our lawyers. The coroner and the police have done their jobs but the financial side is very complicated.

“Chris owed substantially less that the £3 million mentioned at the time and so it seems even less likely that the debts made him act in that way.

“He was obviously under tremendous pressure and we want to know who was applying it, why and whether he was mentally ill. We owe it to Kirstie and Jill to get the truth.

“He was a good actor but I still cannot square the happy picture of the family at a barbeque with what he did hours later.”

Mr Foster said agents acting for HSBC, the bank that held the mortgage on Osbaston House, would soon be submitting plans to the local council to knock down its remains and build a similarly sized luxury property on the front lawn.

He added: “They have offered to put a memorial garden in the grounds which the family would have access to but my mother said no. However there is about two tons of rubble from which the remains of Kirstie could not be completely recovered that we would like buried in the grounds.

“My mother wants it buried in the wood where Kirstie loved to ride. We want to make it a small religious occasion for the family with a vicar saying a few words. The request is being considered by those acting on behalf of the bank that now owns the land.”

Mr Foster disclosed that the remains of Osbaston House had become a magnet for ghouls with a video of the inside of the property appearing on YouTube. “I even had to rescue the name plate because people were trying to pull that off,” he said. Mr Foster said the police still had more than 700 personal items from Osbaston House that included the recently bought laptop of his brother and its hard drive.

Det Supt Jon Groves, who headed the West Mercia Police investigation into the killing of Jill Foster and her daughter and the suicide of her husband, said today: “We are in consultation with legal representatives of both the family and other interested parties in this case. The return of any property we retain is part of those discussions.” A fund started in memory of Kirstie is less than £200 short of its initial £2,000 target with the money going directly to the charity Riding for the Disabled.

A trophy bought with money collected at her funeral will be presented in her memory at their national championships in July.

Mr Foster has put his own family’s home up for sale.

“We will never forget what has happened but we need to make a fresh start and get on with our lives,” said.