He had long-lasting professional working relationships with a number of other British screenwriters and producers, notably Brian Clemens, Terry Nation, Monty Berman and Richard Harris, with whom he developed several programmes.

[1] Following a brief spell as a professional footballer with Leyton Orient,[2] Dennis completed his National Service with the Royal Air Force where he met Tony Williamson, with whom he formed an amateur writing partnership.

Dennis did not desire a career in business and tried to break into the entertainment industry through performance, forming a comedy double act with Benny Davis, now a journalist living in Spain.

[3] Spooner then turned to writing and began selling half-hour comedy scripts to the BBC TV comedian Harry Worth.

While his work in the spy fiction genre was the dominant feature of his writing career, Spooner also made several key contributions to children's drama.

After Spooner befriended Gerry and Sylvia Anderson in the early 1960s, they offered him a chance to write for their new Supermarionation puppet TV series, Supercar.

Although Thunderbirds was the last major work that he did for the Andersons, he returned in the 1970s to write single episodes of the more adult-oriented UFO and The Protectors.

His final work for the Andersons was to write some additional scenes required to knit the first and 17th episodes of Space: 1999 into a feature-length release, known as Alien Attack.

The BBC's episode guide notes that "it is for its innovative use of humour that The Romans will always be best remembered, and in this respect it represents a worthwhile attempt at finding new dramatic ground for the series to cover".

In sustaining the notion for a full serial, Spooner gave birth to an approach to historical events that has continued through to the most recent series of the programme.

At the behest of the producer Verity Lambert, he and Terry Nation (also Survivors and Blake's 7) each wrote half of the longest Doctor Who serial in history, The Daleks' Master Plan.

[citation needed] His final assignment on the programme was to solve problems with the script for the new Doctor, Patrick Troughton, in the serial The Power of the Daleks.

Enticed by the prospect of working on a programme that would receive attention in the lucrative American market, Spooner left Doctor Who to help Nation write the majority of the scripts for The Baron in 1966.

This allowed him to be one of the most prolific writers on The Avengers during the Tara King era, and to successfully submit scripts to Paul Temple and Doomwatch.