After reading English at Liverpool University, Thomas gained national attention when her play, Shamrocks and Crocodiles, won the John Whiting Award in 1985.

[8] On 23 November 2016, the BBC announced a three-year deal with Neal Street Productions, commissioning a seventh, eighth and ninth series, all with Christmas specials.

A production of the musical Gigi was newly adapted by Thomas and ran at the Kennedy Center in January 2015, and then on Broadway, closing in June 2015.

[10] In January 2019, Thomas was presented with the Outstanding Contribution to Writing Award by the Writers' Guild of Great Britain for her body of professional work.

[11] In December of that year, Thomas was a guest on BBC Radio 4's Desert Island Discs, selecting music by Joni Mitchell, The Beatles and Gabriel Fauré, among others.

The film stars Jennifer Saunders, Bally Gill, Russell Tovey, David Bradley, Derek Jacobi, and Judi Dench and was directed by Richard Eyre.