In 2010 she was writer and executive producer of a major revival of the classic British television drama series Upstairs, Downstairs for the BBC. In 2011 she wrote and co-produced an adaptation of the Call the Midwife trilogy of books by Jennifer Worth.[4] The series achieved record viewing figures for the channel.[5] A second and third series aired in subsequent years. In February 2014 BBC announced that a 2014 Christmas Special and a fourth series had been commissioned.[6][7] A fifth series was commissioned for 2016, shortly after series four was done filming.[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.[9] Having ordered series ten and eleven, and despite COVID-19 pandemic, the BBC announced in April 2020 that it had commissioned series 12 and 13, taking episodes into 2024.
In March 2008, she received the Best Writer award at the UK Royal Television Society awards for her work on Cranford. In April 2008 she received the Best Writer award at the UK Broadcasting Press Guild Awards for her work on Cranford, Ballet Shoes, and Lilies. She was nominated for two BAFTA TV Awards for Cranford as well as a Primetime Emmy. In November 2008 she received the Writers' Guild of Great Britain award for Best TV Series for Cranford. In 2011 she received a Primetime Emmy nomination for Upstairs Downstairs. In December 2012, the annual UK 'Women in Film and Television' awards presented her with the Technicolor Writing Award in recognition of her contribution to the industry.
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]