Smith came to prominence on television for her roles in comedy shows Two Pints of Lager and a Packet of Crisps, Love Soup, Gavin & Stacey, Grownups and Benidorm. She has most recently starred in television dramas like Mrs Biggs, for which she won the BAFTA TV Award for Best Actress for playing Ronnie Biggs' wife, The 7.39 and Cilla, where she played Cilla Black. Her film credits include Tower Block, Quartet, Powder Room and The Harry Hill Movie.