The frontrunner to succeed Theresa May in little over a fortnight urged European leaders to „look deep into our eyes“ and understand that the UK will leave the EU with or without an agreement on Halloween, if he becomes prime minister.

The warning, in an interview with The Sunday Telegraph, will rankle in Brussels where EU figures insist they will not re-open the exit deal agreed with Theresa May. Mr Johnson hopes to secure changes by making clear that he will walk away if Brussels refuses to budge, after Mrs May failed to deliver on a similar promise in March.