I'm Sorry, I'll Read That Again

I'm Sorry, I'll Read That Again (often abbreviated as ISIRTA) was a BBC radio comedy programme that was developed from the 1964 Cambridge University Footlights revue, Cambridge Circus., as a scripted sketch show. It had a devoted youth following, with the live tapings enjoying very lively audiences, particularly when familiar themes and characters were repeated; a tradition that continued into the spinoff show I'm Sorry I Haven't a Clue.

The show ran for nine series and was first broadcast on 3 April 1964, a pilot programme having been broadcast on 30 December 1963 under the title "Cambridge Circus", on the BBC Home Service (renamed BBC Radio 4 in September 1967). Series 1 comprised three episodes. Subsequent series were broadcast on the BBC Light Programme (renamed BBC Radio 2 in September 1967). Series 2 (1965) had nine episodes, series 3 (1966) and series 6 through 8 (1968 through 1970) each had thirteen episodes, while series 4 (1966–67) and 5 (1967) both had fourteen episodes. After a three-year hiatus, the ninth and final series was transmitted in November and December 1973, with eight episodes. An hour-long 25th anniversary show was broadcast in 1989, comically introduced as "full frontal radio".

The title of the show derives from a phrase commonly used by BBC Announcers in the age of live radio, following an on-air flub: "I'm sorry, I'll read that again." Basing the show's title on the phrase used to recover from a mistake set the tone for the series as an irreverent and loosely produced comedy show.

I'm Sorry I Haven't a Clue, an unscripted comedy panel game which is a spin-off from ISIRTA, was first produced in 1972 (invented by ISIRTA regular Graeme Garden, who was anxious to develop a comedy format that didn't involve a script deadline each week).