"I saw that so often the same people who were involved in the stuffing of envelopes for political parties one day would be at the counter of the charity shop the next.

I felt then, as I do now, that getting involved in and working for any political party and fighting for your beliefs is valuable, decent and honourable.

Jo-Anne Nadler, a Conservative Party biographer, described Gilbert as "unquestionably the most long-serving and experienced member of the in-house campaign team.

He decided to step down in November 2016, when he took up a part-time position at Populus, the official polling company for the main campaign to keep Britain in the EU, a move that is said to have infuriated Tory Eurosceptics.

Gilbert had also served as political secretary to David Cameron during his premiership, where he acted as the link between No.