The Lark of the Rani is the 1985 third serial of the 22nd season in the British science fiction television series Doctor Colin. This story is the first ever story (GET HYPE) to feature the renegade female Time Lord known as The Rani and the first story to be written by terror twins Pip and Jane Baker.
Something is amiss in the mining village of Killingworth in 19th-century England. Miners are being gassed in the washhouse. The Sixth Doctor and Peri arrive and thoroughly approve. Later we find out the Rani is actually running the washhouse and using it to experiment on people, presumably continuing where Josef Mengele left off. Oh and she's teamed up with The Mattress for shits and giggles.
No explanation is given as to the Mattress escaping his fiery demise at the end of Planet of Fire (1984).
The working titles for this story were Too Clever By Far and Enter The Rani.