Prequel: the Sequel Trivia Quiz

Answer: Torchwood

"Torchwood" is both a spin-off and an anagram of "Doctor Who". Dealing with the alien-hunters of the Torchwood Institute based in Cardiff, the programme starred John Barrowman as Captain Jack Harkness, who originally appeared in the first series of the revived "Doctor Who" in 2005.

Answer: Endeavour

Robbie Lewis was the down-to-earth sergeant in detective series "Inspector Morse" which ran from 1987 to 2000, culminating in Morse's death from a heart attack. Lewis, played by Kevin Whately and latterly promoted to inspector, went on to lead his own murder investigations in the eponymous sequel which came to an end in 2015.

The prequel "Endeavour" was first shown in 2012. Starring Shaun Evans as young detective Endeavour Morse, the programme covers the second half of the 1960s and early 1970s and is perhaps darker than the other two, featuring high-level police corruption.

Answer: Grace & Favour

Sitcom "Are You Being Served?", featuring the staff of the men's and women's clothing departments of London department store Grace Brothers, ran on the BBC between 1972 and 1985. The sequel "Grace & Favour", released internationally as "Are You Being Served? Again!", took up the story following the death of Young Mr Grace. On finding that he had invested their pensions in a country house that they were not permitted to sell, the staff decided to run the place as an inn. Twelve episodes of "Grace & Favour" were made, being shown in 1992 and 1993.

Answer: C.A.T.S. Eyes

"The Gentle Touch", shown between 1980 and 1984, was the first British TV show to feature a female detective in the main role. Jill Gascoine starred as Detective Inspector Maggie Forbes, who also featured in follow-up series "C.A.T.S. Eyes" about an all-female team of detectives working covertly for the Home Office.

Answer: Tucker's Luck

Children's TV drama "Grange Hill", centred on a London comprehensive school, ran from 1978 until 2008. Rebellious pupil Peter "Tucker" Jenkins, played by Todd Carty, featured in the first four series of "Grange Hill" and then in spin-off series "Tucker's Luck", which dealt with his and his friends' attempts to make their way in the world after leaving school. "Tucker" featured in the last ever episode of "Grange Hill", persuading his nephew not to make the mistake he had made by leaving school too early.

Answer: Holby City

"Casualty", set in the Emergency Department of Holby City Hospital, was first broadcast in September 1986 and went on to become the longest-running primetime medical drama in the world. "Holby City", which concentrates on other departments in the hospital, began as a spin-off of "Casualty" in 1999 and the two programmes have been shown in tandem ever since.

As they have always been filmed in different locations, there is less cross-over between the two shows than might be expected.

Answer: Softly, Softly

"Z-Cars", first shown on the BBC in 1962, centred on the work of mobile police officers in the fictional Merseyside district of Newtown. Though later revived, its original run ended in 1965. Replacement spin-off "Softly, Softly" ran from 1966 until 1969. Concentrating on the work of a regional crime squad in "Wyvern", in southwest England, the show starred Stratford Johns and Frank Windsor, whose characters Detective Chief Inspector Charles Barlow and Detective Inspector John Watt had been mainstays of Newtown CID. Further spin-offs were "Softly, Softly:Taskforce", "Barlow at Large" and "Jack the Ripper" and "Second Verdict", in which Barlow and Watt investigated unsolved mysteries and possible miscarriages of justice.

Answer: Pardon the Expression

Today best remembered for playing Captain Mainwaring in "Dad's Army", Arthur Lowe first became a household name when playing Leonard Swindley, manager of drapery store Gamma Garments, in "Coronation Street". He continued in this role in sitcom "Pardon the Expression", the first-ever "Coronation Street" spin-off, and then in "Turn Out the Lights", a spin-off of the spin-off.

Answer: Rock and Chips

"The Green, Green Grass", a sequel to long-running comedy "Only Fools and Horses", starred John Challis and Sue Holderness as Boycie and his wife Marlene, Peckham natives forced to flee to the country to escape the vengeance of the gangster Driscoll brothers. Boycie featured as a schoolboy in prequel "Rock and Chips", set in 1960 and commissioned following the success of "The Green, Green Grass". Three episodes were made, writer John Sullivan dying five days before the final one was broadcast.

Answer: Ashes to Ashes

"Life on Mars" tells the story of Sam Tyler, played by John Sim, a Manchester police officer who is knocked down by a car in 2006 and wakes up in 1973. Tyler finds himself working under the command of "old style cop" Gene Hunt, played by Philip Glenister.

In the sequel "Ashes to Ashes", London detective Alex Drake, played by Keeley Hawes, is shot in 2010 and wakes up in 1982. She then has to work with Gene Hunt and his colleagues Ray Carling and Chris Skelton, whom she has read about in reports written by Sam Tyler.

In neither series is it clear whether the protagonist is actually dead.

Answer: Going Straight

Norman Stanley Fletcher and Lenny Godber, played by Ronnie Barker and Richard Beckinsale, shared a cell in Slade Prison in BBC comedy series "Porridge". "Going Straight" took up their story on their release from prison. Only six episodes were made, Beckinsale dying of a heart attack at the age of 31 shortly before the programme received a BAFTA award.

Answer: Count Duckula

Animated series "Danger Mouse", featuring David Jason as 'the world's greatest secret agent' and Terry Scott as his hamster sidekick Penfold, ran on British television between 1981 and 1992 and was the first British cartoon to be shown on Nickelodeon. "Count Duckula", also voiced by David Jason, was a vampire duck with a lisp and a desire to appear on television. Given his own spin-off show on Nickelodeon, the Count was transformed into a vegetarian with ketchup running through his veins.

Answer: Thomas & Sarah

"Upstairs Downstairs" ran on British television from 1971 to 1975, following the Bellamy family of Eaton Square, Belgravia and their servants from 1903 through to 1930. Chauffeur and maid Thomas and Sarah, played by John Alderton and Pauline Collins, had left the house in 1910.

Their own spin-off series ran for 13 episodes starting in 1978. Plans for a second series were derailed by a TV strike in 1979.

Answer: George and Mildred

Comedy "Man About the House", starring Richard O'Sullivan, Sally Thomsett and Paula Wilcox as student chef Robin Tripp and his two female flatmates, ran from 1973 to 1976 and was remade in the USA as "Three's Company". Landlord George Roper and his wife Mildred were played by Brian Murphy and Yootha Joyce, who went on to star in their own sitcom in which the Ropers moved into an upmarket housing estate. "George and Mildred" ran for five series.

Answer: Kessler

"Secret Army", a co-production made by the BBC and Belgian broadcaster BRT, dealt with Lifeline, a resistance unit helping Allied airmen evade capture and return to Britain. Ludwig Kessler was a Gestapo officer tasked with closing down the organisation.

The series was broadcast between 1977 and 1979. In the eponymous sequel, made in and set in 1981, Kessler, now known as Manfred Dorf, was part of a fugitive Nazi organisation, the Kameradenwerk. He was played in both series by Clifford Rose.