In the early 1980s Robert Love , then controller of drama at Scottish Television, hit upon the idea of making a series about a Glasgow detective. At the same time, he was working with a new writer, Glenn Chandler , whose fresh approach he thought would be ideal.

Robert Love explains: “I wanted to find something that the ITV network couldn’t refuse – a detective series and a thriller. I felt that Glasgow had particularly colourful aspects, it was a kind of gothic city and Glenn’s imagination was always fired by the exotic and the colourful so I thought that Glasgow would be the perfect setting.”

Glenn set to work, visiting Glasgow’s Maryhill cemetery in search of inspiration – and finding names for his characters on the gravestones. The result was Killer, a three-part thriller broadcast in 1983, featuring tough Glaswegian detective Jim Taggart, played by Mark McManus and his sidekick Peter Livingstone (Neil Duncan).

Killer was broadcast to great critical acclaim and the ITV network quickly decided that it wanted more. In 1985, the name of the series became Taggart.

Although Mark McManus was synonymous with the series, becoming almost a folk hero, his death in 1994 did not mean its end. Thanks to the popularity of his fellow detectives at Maryhill CID and scripts that kept viewers guessing to the end, Taggart continued to win over the hearts of British viewers and fans around the world.

Explains Glenn Chandler: “We knew that Mark was going to die and we also knew that Mark wanted us to carry on the series after him. I wrote the episode in which he died. It was a hard one to do – we had to begin with Taggart’s funeral then go on to another whodunit story and carry it forward.

“A lot of my inspiration comes from true crime and I love taking stories and putting them into secret worlds. We never rested on our laurels and I think Taggart continues now after 20 years because of the strength of the team of people and the new blood coming into it.”

James Macpherson played Mike Jardine for 15 years, rising through the ranks to become DCI after Taggart’s death. He left the series in 2002. Blythe Duff and her character Jackie Reid have appeared in more than 40 films spanning longer than Mark himself, and Colin McCredie has clocked up more than 30 films in the role of DC Stuart Fraser.

Newer faces to the series have also become firm favourites - ladies’ man DI Robbie Ross, played by John Michie and tough talking new boss DCI Matt Burke, played by Alex Norton. Both actors ironically appeared in Taggart earlier in their careers.

The series is famous for attracting the crème of British talent – and has seen some up-and-coming Scottish actors passing through on their way to greatness.

The roll call of famous names includes Robert Carlyle, Peter Mullen, John Hannah, Dougray Scott, Ken Stott, Isla Blair, Jill Gascoine, Annette Crosbie, Alan Cumming, Ann Mitchell, Hannah Gordon, Barbara Dickson, Jason Isaacs, Amanda Redman, Clare Grogan and Diane Keen – to name but a few.

Alan Cumming, now a major player in Hollywood, says: “I was 21, it was my first year after drama school and a part in Taggart was the big thing you wanted to get. When I got it I was jumping up and down. I have lots of memories, especially because I had take all my clothes off in one scene!”

During the 20 years, the series has encompassed the deaths of two other major characters – Chief Superintendent McVitie, played by Iain Anders and Robert Robertson who played pathologist Dr Stephen Andrews. The 20th anniversary season sees the arrival of a new forensic expert, Gemma Kerr, played by Lesley Harcourt.

The murders and forensic examinations call for gruesome and lifelike special effects. Dealing with detached limbs, gunshot wounds, strangulation victims and congealed blood are all in a day’s work for the skilled make-up team.

After 18 years, Taggart entered the record books as the longest-running police drama currently on TV. Z-Cars ran for 18 years until 1978 and The Bill was first shown in 1984.

The highest-ever audience for Taggart was 18.3 million viewers for a 1992 episode, entitled ‘Violent Delights’. It remains one of ITV1’s most successful dramas, consistently attracting an audience share of between 31 and 34 per cent.

Taggart is also one of British TV’s top exports, bringing Glasgow on to the international stage. Since the series began it has been sold or broadcast in more than 80 countries spanning the globe, from Iceland to New Zealand and from the USA to Japan. Both subtitles and dubbing are used to bring the characters to life for overseas audiences.

Famous fans include the director Ken Russell and crime novelist PD James – and even the Queen Mother, as Robert Love explains:
“I had a telephone call from the Equerry to the Queen Mother who said she had unfortunately missed an episode and would we kindly send it for her to view. I thought I was having my leg pulled at first but we sent the tape to Clarence House and about a month later a very nice letter came back saying the Queen Mother had enjoyed the episode and was looking forward to the next one!”

The new production team, executive producer Eric Coulter and series producer Graeme Gordon, took over the programme in 2001, overseeing the introduction of Burke played by Alex Norton. In 2003 they secured their biggest commission yet for the series – six feature-length episodes, making a total of nine hours of drama.

By sticking to the original spirit of Taggart – a great whodunit story, strong characterisation and the filmic backdrop of Glasgow - while breathing new life into it, the team hopes this national institution will remain an on-going part of TV history for the 21st century.