Former Doctor Who showrunner Russell T Davies has announced plans to release "the final Sarah Jane adventure" this Sunday.

In 2007 Davies created spinoff show The Sarah Jane Adventures focusing on former companion Sarah Jane Smith (Lis Sladen), who travelled with the third and fourth Doctors in the 1970s.

Aimed mainly at a younger audience, the show ran for five series until Sladen's death from cancer in 2011 at the age of 65, just two months after she had been diagnosed.

Writing on Twitter, Davies revealed that the special adventure - Farewell, Sarah Jane - would be released online at 5pm on Sunday and has been made "with the blessing of Lis's family".

Farewell, Sarah Jane will serve as a warm-up to a mass fan rewatch of the series four finale later on Sunday.