Sheridan Smith, OBE played Lucie Miller, companion to the Eighth Doctor, who debuted in the Big Finish production for BBC Radio, Blood of the Daleks. She can therefore fairly be said to have played a "radio companion", not merely an audio one. In fact, she is certainly the only actor to originate a recurring, lead role in Doctor Who on radio.
Outside Doctor Who, she is likely best known as one of the stars of the long-running programme Two Pints and a Packet of Crisps alongside Kathryn Drysdale. She also starred with Paul McGann in the 2010 Jonathan Creek Easter special, "The Judas Tree".
Smith is a double Laurence Olivier Award winner. Her first Olivier was for her work as the first British Elle Woods in the original West End run of Legally Blonde, co-starring Peter Davison. Her second came from the 2011 West End revival of Flare Path, which also starred James Purefoy, Sarah Crowden, and Clive Wood. In 2013, she picked up a BAFTA for her performance in Mrs Biggs, a production in which she starred opposite Daniel Mays.