The four soldiers died at Deepcut Barracks between 1995 and 2002

Frank Swann was hired by the families of the soldiers, who all died from gunshot wounds at Deepcut barracks in Surrey.

He left the barracks on Thursday afternoon having carried out forensic and ballistic tests, but will not present his report for several weeks.

As he left the site he said he knew the causes of the deaths, but could not yet reveal them.

The dead soldiers Pte Sean Benton, 20, from Hastings, East Sussex Pte Cheryl James, 18, from Llangollen, North Wales Pte Geoff Gray, 17, from Seaham, County Durham Pte James Collinson, 17, from Perth, Scotland

Four soldiers died from gunshot wounds at the barracks between 1995 and 2002.

In each case the Army attributed the deaths to suicide, but the families of all four victims have disputed that verdict and accused the Army of a cover-up.

Mr Swann has tried to reconstruct the exact circumstances surrounding each of the deaths to assess whether the gunshot wounds could have been self-inflicted.

Frank Swann says he knows how they died

As he left Deepcut he said: "As to whether the injuries were self-inflicted, were caused by another person or were an accident - we do know the answer but we cannot say."

Geoff Gray, the father of one of the recruits who died, says the families will wait to see the report before deciding whether to make the findings public.

He met Mr Swann at the gates of the barracks and said: "I just wanted to be here to thank Frank for all his hard work in our search for the truth."