My initial research was based on cuttings from newspaper archives. The story of the 'remote executive' and how he murdered his mistress was national news back in March 1971 when Tim's case came to trial, generating some salacious (and speculative) headlines. A contact on the Daily Telegraph helped with the first trawl of cuttings, letters to the Northern Echo unearthed more local coverage and a visit to the central library in York produced the most in-depth coverage of all, as the case was reported on in minute detail by the York Evening Press, whose back issues are kept there on microfiche.

That was just the start. Once I'd committed to doing the book, I contacted the public records office, who told me that Tim's file was closed to public inspection until 2056. Fortunately, his case went to appeal and I was able to procure a transcript of that hearing, which contained vital forensic evidence as well as other information that hadn't come out in the press. I also hired a researcher to look up records for me and go through indexes. She produced birth certificates, marriage certificates and death certificates, from which it was possible to glean an enormous amount of information. But I needed to hire a private investigator to get my biggest scoops - the interviews with Strick Carter, one of the two former detectives who arrested Tim, and Gilbert Gray, the QC who defended Tim at his trial. The private investigator I used was David Farrar, a former member of York CID, and through him I was also able to find Harry Codling, a PC who was on attachment to CID at the time .

The internet is, of course, a crucial research tool for any writer, and through doing web searches I was able, eventually, to locate Tim's sister, Antonia, who told me so much about her brother that I didn't know. I also put out an appeal for information on a Northallerton website and was contacted by a woman who had been a schoolfriend of the daughter of the murdered woman. I used the internet to do virtual tours of the Exeter University campus, locate friends of mine and Tim's from the old Barton Place days and to get in touch with Pickerings, the company Tim was a director of. Pickerings put me in contact with Tim's boss and personal friend, Christopher Fothergill, who now lives in Switzerland, and Dave Upton, a colleague of Tim's, who was the last person to see him before he died. I met and interviewed Christopher at his London club and managed, after many letters and phone calls, to speak to Dave - who, in turn, gave me the name of another former colleague of Tim's, Derek King. And so it went on.

At that stage, the problem I had was deciding when to stop. I was obsessed with getting to the bottom of things and every interview produced fresh leads and more intriguing questions. There were hints of a coverup, of more scandal and I could have gone on digging, but I had a deadline to meet. Also, I had to question my objectives: I wasn't out to expose other people's lives, only Tim's. You have to draw a line somewhere. My biggest regret, at the time, was that I didn't manage to find the daughter of the woman Tim murdered. She, above all, was the person I wanted to talk to but she had effectively disappeared after Tim's arrest and no-one, not even her schoolfriend, knew where she was. It was frustrating not to find her but with nothing to go on, I had no option.