In 2000, he was appointed Senior Policy Adviser "Best Value" to Mayor of LondonKen Livingstone following his election.[4] He was reported to be one of Livingstone's closest advisors, enjoying "virtually immediate access to the mayor".[5] After Livingstone's re-election in 2004, Coleman's salary was raised to £111,000 a year; higher than that of the mayor himself.[6] Coleman was the only senior adviser to continue serving under Livingstone's successor Boris Johnson, who referred to him as "Comrade Coleman".[7]
Coleman was appointed by Jeremy Corbyn to be the Labour Party's Director of Policy following Corbyn's victory in the Labour Party leadership election.[8] Alongside fellow former Livingstone aide, Simon Fletcher, Coleman was dubbed one of the "Mensheviks" in Corbyn's inner circle.[9] He resigned in January 2016[10] following reports of disagreements with Corbyn's head of strategy and communications Seumas Milne and Andrew Fisher, the leader’s policy adviser.[11]
In 2016, he was appointed as an adviser to London Mayor Sadiq Khan's transition team, but resigned just three weeks into the job following reports that Khan was unwilling to extend Coleman's contract beyond the three-month transition period.[12]
^Boothroyd, David (2017-05-18). "Maida Vale Ward 1964-". Westminster City Council Election Results. Archived from the original on 18 May 2017. Retrieved 2022-08-11.