He was the Member of Parliament (MP) for St Austell and Newquay from 2015 until 2024 when he was defeated in the 2024 United Kingdom general election by Labour candidate Noah Law.

[11][12][13] Double previously chaired the now defunct All Party Parliamentary Group Ocean Conservation, working with Cornish charity Surfers Against Sewage.

He also sat on the Parliamentary Space Committee where he promoted Newquay as a frontrunner for the location of the UK's first spaceport.

[21] In August 2019, Double was appointed Parliamentary Private Secretary to the Department of Health and Social Care.

[23] On 17 September 2021, Double was appointed an Assistant Government Whip in the second cabinet reshuffle of the second Johnson ministry.

[24] In July 2022, he was appointed Parliamentary Under-Secretary of State at the Department for Environment, Food and Rural Affairs.

[27] On 28 October 2022, Double was made Government Whip to the Ministry of Defence by new Prime Minister Rishi Sunak,[28] and King Charles III accordingly named him a junior Lord Commissioner of the Treasury by letters patent dated November 28, 2022.

[30] He was listed in an article in The Daily Telegraph which criticised the practice of MPs employing family members, on the lines that it promotes nepotism.