A “maverick” Labour Party poses a greater risk to the Square Mile's future than Brexit, the City minister said on Wednesday, as he called for financial executives to wake up to the risks posed by having Marxist Shadow Chancellor John McDonnell in power.

John Glen, the ruling Conservative Party’s Economic Secretary for the Treasury, said it was “unbelievable” that the opposition Labour Party’s McDonnell had both “hailed Marxism” as a viable future for the country and had committed to overthrowing capitalism.