 However, he subsequently left UKIP in December 2018.He became the leader of the Brexit Party in March 2019.On 4 October 2019, Rory Stewart, who had been a Conservative MP and came fifth in the 2019 Conservative Party leadership election, but was then expelled from their Parliamentary group for his opposition to a "no deal" Brexit and was sitting as an independent MP, announced he was standing as an independent candidate for the London mayoralty.