It was 25 years ago today: Watch it, lads; here comes 'The Sweeney'

'A sad squandering of brain-power," said the Daily Mail's critic after viewing ITV's Armchair Cinema offering on 4 June 1974. Regan, a 90-minute film written by Ian Kennedy Martin and produced by Euston Films, was about a maverick Flying Squad DI (John Thaw) and his chirpy partner, Carter (Dennis Waterman). Police drama would never be the same again.

Regan and Carter returned in a 14-part prime-time series, The Sweeney, the following January. They swore and drank and aimed punches and guns. They drove quickly and braked sharply on the rundown Docklands streets. There was a very fine line between them and the villains. "A very superior police thriller," said the Daily Telegraph. But Clive James found it "boring and unsettling at the same time" (Observer), and the Sunday Telegraph hated the "sheer banality of all that kicking and punching and squealing of tyres".

The Mail warned that the violence might be "moderately detestable" to some people - Mary Whitehouse obliged - and longed for "the extra ounce of care, accuracy and concern distinguishing tamer rivals such as Softly Softly". During the course of three more series, The Sweeney oversaw the demise of that rival - the BBC's sequel to the ground-breaking Z Cars - and saw off many blatant imitations of its own "shut-it-get-your-trousers- on-you're-nicked-son" grit.

Ian Kennedy Martin, whose brother Troy was responsible for Z Cars, says the idea came about when he was watching its "dying embers". Softly Softly had "become like a soap," he says: "It just didn't reflect what was going on in the police. At that time, drugs were becoming a big issue and armed robbery was the major crime in London. None of this was seen. It was all internecine rows at HQ and people talking about budgets. We needed two cops running on the streets."

Dennis Waterman recalls that, at first, the police "weren't happy with the language and the levels of violence. We were portaying them as real people, not as paragons of virtue." But Scotland Yard quickly realised it would be to its benefit to get involved. "We had an unofficial and an official adviser," says Waterman. "The official adviser worked out of Scotland Yard. He would say that to get hold of a gun you'd go and ask your boss and he'd ask you what it's for and then you'd sign 17 forms for it. The unofficial adviser would say 'Bollocks. What you do is go and get a gun out of the safe and if the job's risky you just take it with you'."

Kennedy Martin, who sold the scriptwriting rights after the pilot but retained an involvement with the storylines, says his aims were to "fix it geographically and to show violence for what it was". The final episode was shown in December 1978. "John and I had long conversations about whether we should do some more," says Waterman. "But there are only so many murders and bank robberies and rapes you can do." MAEVE WALSH