On a big screen yards from Downing Street, Marco Rubio was midway through a paean to western civilisation when the sound went down, and not for the first time.
“I don’t know who you are mate but I agree with you,” shouted a woman, draped like so many of those on the self-styled “Unite the Kingdom” march in the flag of St George and soaking up the atmosphere at what has emerged as the nearest thing to a far-right Glastonbury.
