He also served as a magistrate, initially the youngest in Essex when appointed in 1988. He served for 21 years before transferring to the supplemental list in 2009, in order that he could stand for the European Parliament and to avoid any perception of conflict of interest.
He was 4th on the Conservative list for the East of England region in the European Parliament elections in 2009 and 2014, but only 3 Conservatives were elected on each occasion. He took his seat in 2017 after fellow MEP Vicky Ford was elected as an MP in the general election.[8]
Flack sat on the European Parliament's Committee on Regional Development (REGI).[9] He served as the Regional Development Spokesman for the Conservative Party.[10] He was also a substitute member of the Parliament's Committee on Fisheries (PECH).[11]
Flack is an active animal welfare campaigner, and has co-hosted a roundtable event on fur labelling problems in the EU market.[12] He was a member of the European Parliament's Animal Welfare Intergroup.[13] In 2019 he was appointed as a Patron of the Conservative Animal Welfare Foundation in acknowledgement of his commitment to animal welfare reform.