He chaired the Joint Intelligence Committee from 2019 to 2023 and served as the British Prime Minister's representative on Afghanistan from 2021 to 2022 concurrently.

Following these events Gass posted his views from Tehran on the social networking site Twitter, commenting on the Iranian regime's record on human rights, political prisoners and freedom of speech.

In December 2010, Gass's digital activities caused mild uproar among Iranian politicians, who called for his expulsion after he highlighted the case of human rights lawyer Nasrin Sotoudeh in an article posted on the British Embassy in Iran website.

[6] The Foreign and Commonwealth Office defended Gass's comments, which gained widespread approval from his Iranian reformist followers on Twitter.

[7] After serving in this post for 18 months he returned to the FCO in London as Director General, Political, and the Prime Minister's Special Representative for Afghanistan and Pakistan.