Brian Clemens: Writer and producer who made 'The Avengers' an emblem of the Swinging Sixties and created 'The Professionals'

His output was so prolific during the 1950s and 1960s that he frequently used the pseudonym 'Tony O'Grady'

Brian Clemens: His output was so prolific during the late 1950s and 1960s that he frequently used the pseudonym 'Tony O'Grady' (Getty)

In 1956 Brian Clemens was hired as a writer by the independent producers Edward J and Harry Lee Danziger, who churned out "B" features at Merton Park Studios in south London. Danziger productions were always economical, and it was not unusual for him to be presented with sets and props inherited from an earlier film and told to dream up a story involving, say, a German submarine, the Old Bailey and some Father Christmas outfits; he became an expert at devising bizarre plots, a talent which would serve him well when he began writing for The Avengers, the series that made his name.

Born in Croydon, he began writing when he was five, with a little story about a badger and a snake; when he was 11 his father bought him a typewriter, on which the young Clemens bashed away until in 1943 he sold his first paid work, for one guinea, to a hospital magazine.

In the confusion of wartime he managed to avoid formal education, learning from books at home and visits to the cinema. During National Service he was a firearms instructor, then became a copywriter at J Walter Thompson's.

In 1953 BBC television accepted his play for two characters, Valid For A Single Journey, and he was on his way. In 1956 he was hired to write Operation Murder, one of the Danzigers' "B" films. He contributed dialogue and storylines to a couple of dozen of these pictures – in 1961 alone he penned four – while he wrote some dozen episodes for the Danzigers' private detective TV series Mark Saber.

His output was so prolific during the late 1950s and throughout the 1960s that he frequently used the pseudonym "Tony O'Grady". During 1960 he adapted Edgar Allan Poe's macabre The Tell-Tale Heart for the cinema, wrote "Nest Of Four" for Armchair Theatre and adapted Julius Caesar into modern dress for the Danzigers' An Honourable Murder.

He cut his TV teeth properly on the first season of Danger Man (1960), writing with producer Ralph Smart for this fast-moving secret agent series with its charismatic star, Patrick McGoohan. Simultaneously he was writing for another Patrick, Macnee, on The Avengers, for which he wrote the pilot episode, soon becoming story editor and co-producer.

The 'Avengers' episode 'Fire and Brimstone'; Diana Rigg's self-designed costume led to the episode being banned in the US

By 1962 Macnee's ambiguous secondary character, John Steed, had assumed the leading role, and the show had evolved from a monochrome "film noir for television" into the colourful, insouciant surrealism that became its trademark. Clemens wrote some 28 scripts, including A Touch Of Brimstone, which achieved cult status on the basis of Diana Rigg's kinky outfit (which Rigg designed herself) when as Emma Peel she joined a modern Hellfire Club. The episode was banned in the US. The final Avengers episode, transmitted in 1969, was appropriately entitled Bizarre.

For his 1962 foray into mainstream cinema, Station Six Sahara, Clemens had shared the writing credit with Bryan Forbes. Seth Holt's film was a torrid character drama that created a sense of claustrophobia under an open sky.

During The Avengers run he amused himself contributing scripts to the BBC's shot at camp escapism, Adam Adamant Lives! in which an Edwardian gentleman adventurer is released from suspended animation to fight crime in the "swinging" London of 1966. He also wrote the screenplay for an international co-production known in Britain as The Peking Medallion, starring Robert Stack and Elke Sommer. James Hill, an Avengers stalwart, directed.

At the end of 1969 Clemens co-wrote with Terence Feeley a stage version of The Avengers, with Simon Oates as Steed; it had a short run. Two more plays, Dear Hearts and Where The Wind Blows in 1972 and 1973, made no greater impact. Meanwhile, for the big screen And Soon The Darkness (1970), about two young English nurses in France menaced by a sex killer, brought him together with Albert Fennell and Dr Who writer Terry Nation.

Blind Terror (1971) was an exercise in suspense, masterfully directed by Hollywood's Richard Fleischer, with Mia Farrow as the blind girl threatened by an unseen psychopath; Dr Jekyll And Sister Hyde (also 1971) for Hammer was an ingenious and satisfying variation on a theme, with alert direction from Roy Ward Baker. The script was voted best of the year by the Paris Convention of Fantastic Cinema.

At the end of a busy year, the indefatigable Clemens launched ITC's light-hearted vehicle for Tony Curtis and Roger Moore, The Persuaders and in 1972 he joined actor-turned-writer Richard Waring to create the situation comedy My Wife Next Door. That same year he explored more fresh ground, directing an original screenplay of his own for Hammer Films.

Captain Kronos – Vampire Hunter was a tongue-in-cheek horror movie in a comic-strip adventure style, with the superhero accompanied by a sardonic hunchbacked factotum rejoicing in the name of Professor Heironymous Grost. He made his US TV film debut with a stalker drama, The Woman Hunter, then dreamed up a suitable plot with Ray Harryhausen for the special effects wizard's The Golden Voyage Of Sinbad (1973).

He returned to first principles with an impeccably crafted anthology series for ATV, Thriller. The scripts were good enough to attract the likes of like Stanley Baker and Diana Dors, and a random selection of individual episodes – "One Deadly Owner", "Crazy Kill", "Nightmare For A Nightingale" – vividly conveys the flavour of a series that ran from 1973-76.

The New Avengers (1976) had to seek co-production finance outside Britain, and critical reaction was lukewarm; yet with Steed flanked by action man Gareth Hunt and former model Joanna Lumley as Gambit and Purdey, it had bags of style. In 1977 Clemens' and Fennell's Avengers Mark 1 Productions went into partnership with LWT to create The Professionals, about a fictional undercover security unit, C15, whose macho operatives Bodie and Doyle made actors Lewis Collins and Martin Shaw household names; it was expertly made and packed with fashionable violence.

In 1981 Clemens' name appeared on US television again in Darkroom, an anthology of spooky yarns. Next, he adapted Florence Randall's book The Watcher In The Woods, an unlikely subject for Walt Disney, a strange tale about mysterious forces, ancient rituals and extra-terrestrials. Disney's executives were uneasy with the result – directed in Britain by another Avengers graduate, John Hough – and it was partially re-shot and re-edited. In Timestalkers, an historian of the Old West is transported back to the era of Wyatt Earp and Doc Holliday to face a psychotic gunslinger incarnated by Klaus Kinski.

In 1988 Clemens adapted his novel Blue Blood (German aristocrat investigates murder of film star) for a 13-episode serialisation on Tele-Munchen. The early 1990s found him in the US again, providing scripts for Max Monroe: Loose Cannon, one for Father Dowling Investigates, and the likes of "The Case Of The Glass Coffin" for the new Perry Mason series. For BBC TV and the independent production company Carnival Films in 1995 he created Bugs; his first story, about the remote-controlled sabotage of civilian aircraft, was praised for its narrative pace and jazzy visuals, characteristics that prompted one reviewer to cite The Avengers as the obvious precedent.

In 1999 Clemens devised C15 – The New Professionals for Sky One, Edward Woodward taking on the mantle of Gordon Jackson as the outfit's boss, while in 2010 And Soon the Darkness was remade, with two young Americans in Argentina.

Brian Horace Clemens, scriptwriter, story editor and producer: born Croydon 30 July 1931; OBE 2010; married firstly Brenda (marriage dissolved; two sons); 1979 Janet; died 10 January 2015.

Cy Young died in 2013.