His battered body, clad only in a pair of trousers, was discovered floating in a half-filled bath. He had been repeatedly beaten with a blunt object and had suffered severe fractures to his skull, face and body.
The murder, discovered on Wednesday morning at his rented three-bedroomed house in an affluent suburb of Birmingham, threatens to expose the murkier side of Mr Trigwell's chosen profession.
Mr Trigwell, 44, was a private investigator. Not, it would appear, the type of private eye who spent his time lurking in bushes trying to catch unfaithful husbands or issuing writs to unsuspecting debtors, but a man who lived on the dangerous side of life.
John Clarke, an investigator who used to work with Mr Trigwell at Nationwide Investigations in Birmingham, said his former colleague was known as "Barry the Bastard" by people he crossed.
He recalled: "He really enjoyed snatching children back from abroad after one of the parents had skipped the country. He seemed to live for the adrenaline rushes.
"He was a short, stocky bloke - he looked the classic image of a Chicago gangster. He has been involved in cases all over the world, he has been caught up in some very heavy stuff, but this was supposed to be a quiet patch in his life.
"He charged a lot of money but he was really good at his job. He was a physically strong man. When some of us may have taken a step back for fear of the consequences, Barry would just go for it. Barry has made many enemies in his life."
One of his enemies entered Mr Trigwell's home in the smart cul-de-sac of Fowey Close, Walmley, Sutton Coldfield, on Tuesday evening, probably after his victim returned home at about 7pm from a meal at an Indian restaurant.
The following morning a colleague arrived to pick him up - he was banned from driving - and found bloodstains on the carpet.
Police believe his killer may have dragged the body to the bathroom or Mr Trigwell may have staggered there and later died. His blood-soaked shirt was found discarded in the bathroom.
Police were yesterday tracing Mr Trigwell's clients and examining his files in search of clues. They are also interviewing his colleagues at Nationwide Investigations, one of the country's largest agencies.
Mr Trigwell, married with a 14-year-old daughter, started work as a freelance detective in 1974.
He bought a franchise from Nationwide in Birmingham about four years ago, and employed two other detectives. The agency recovers snatched children, as well as mundane work such as tracing debtors and missing benefactors to wills.
Unusually Mr Trigwell is not listed in any of the professional directories, suggesting that he relies on specialist clients. He is not a member of the Association of British Investigators, which has a code of practice. He told colleagues that much of his past work was in the Middle East and Hong Kong.
A Birmingham-based investigator, who did not want to be named, said: "Trigwell would do anything, and if you start mixing in dangerous company, or where passions run high, you have got to expect your life could be at risk." Another private detective yesterday suggested that Mr Trigwell may have been investigating money launderers.
Norman Smith, the former president of the ABI, said: "This field can be particularly dangerous, particularly when the money is from drugs."
Mr Smith said that despite the industry's media image of investigators tracking down lost millions and solving murders, most of the work of the country's 4,000 detectives involved finding witnesses for insurance claims and issuing writs.
The last investigator whose job apparently cost him his life was Daniel Morgan, who was found in a south London pub car park with an axe embedded in his head in March 1987.
Mr Trigwell's Birmingham colleagues yesterday refused to comment. A spokesman at the firm's London headquarters said: "It's an awful thing - we are all in shock about it, but I'm not going to answer any questions about our business, it's confidential."Reuse content