In 2008 he joined the Special Boat Service, serving for 4 years as a point man and as a sniper, in two further tours of Afghanistan.
[9] Middleton was the Chief Instructor on SAS: Who Dares Wins, a reality high-fitness training television programme produced by Minnow Films for Channel 4, which was first broadcast in 2015.
Mutiny, an adventure/reality crossover show, was screened on UK television in February 2017, with Middleton starring as boat captain alongside eight volunteer participants.
On 14 May 2018, Middleton reached the summit of Mount Everest with Ed Wardle, completing the ascent over a five and a half week period.
[19][20] He left the position nine months later amidst controversy surrounding a comment he made on Twitter, which appeared to compare Black Lives Matter protesters with the English Defence League as extremists and "scum", though he clarified that he was not equating the two groups.
[24] On 8 January 2025, Middleton hinted on X (formerly Twitter) that he would run for Mayor of London for Reform UK in 2028, stating "My country is calling me once again!
[25] On 20 January 2025, Middleton was part of Reform UK's delegation to the second inauguration of Donald Trump in Washington, D.C., in the United States, along with leader Nigel Farage and party treasurer Nick Candy.