They stated: "Dorothy Thornhill overcame tough opposition to become the first directly LibDem mayor in 2002 and she was re-elected in 2006.

"[4] At a Liberal Democrat town hall meeting in Watford, in February 2010, the leader of the party, Nick Clegg was asked whether he felt the Mayor was right to earn the same wage as a member of parliament whether she was "value for money", and in response he named her "one of the best mayors in this country".

[9] She decided not to stand in the 2018 mayoral election and was succeeded by fellow Liberal Democrat Peter Taylor.

[10] As a Liberal Democrat peer, Thornhill led the party's internal review into their performance in the 2019 general election, which was published in May 2020.

In 2023, Thornhill was fined and disqualified from holding or obtaining a driving licence for 6 months for speeding on Hempstead Road in Watford.