Slipback

Slipback is a radio audio drama based on the long-running British science fiction television series "Doctor Who", produced by the BBC and first broadcast in six episodes on BBC Radio 4 from 25 July to 8 August 1985, as part of a children's magazine show called "Pirate Radio Four". It was later released on cassette and CD, most recently by BBC Audio and free with the 27 April 2010 edition of "The Daily Telegraph" newspaper via WHSmith.
Synopsis.
The Sixth Doctor and Peri arrive on a mysterious space liner, where intergalactic policemen are investigating art thefts, a computer is suffering from a split personality and the Captain's disease threatens every living thing on the ship…
Production.
"Slipback" was broadcast on BBC Radio 4, four months after the final episode of "Doctor Who"'s twenty-second season, during the programme's enforced hiatus, the next season not airing for another a year and a half. It was the first "Doctor Who" serial produced as a radio play (an earlier audio production, "The Pescatons", was released as a story record). No further radio productions were mounted until the mid-1990s when Jon Pertwee reprised his role as the Third Doctor in two productions, "The Paradise of Death" and "The Ghosts of N-Space".
Writing.
The story was written by series script writer Eric Saward, whose writing credits include "The Visitation", "Earthshock", "Resurrection of the Daleks" and "Revelation of the Daleks". 
Cast note.
Valentine Dyall played the Black Guardian in the television series. Dyall died in June 1985, a month before "Slipback" aired.
In print.
A novelisation by Eric Saward was published by Target Books in April 1986, the first novelisation of a non-televised "Doctor Who" story. Saward's novelisation expands on the radio play greatly, with an extensive prologue running about a third of the book before the Doctor appears and the adaptation of the radio play storyline begins.
Audio releases.
"Slipback" was released in November 1988 on a double audio cassette along with the 1978 LP version of "Genesis of the Daleks". It was subsequently released as a standalone CD in January 2001.