Britain’s decision to quit the European Union represents a “failure and a tragedy” for the world largest political and economic bloc, its leader Jean-Claude Juncker has admitted as he prepares to lead the EU’s 60th anniversary celebrations in Rome this weekend.

The run-up to Saturday’s celebrations to mark the anniversary of the signing of the Treaty of Rome in 1957 has been marred by deep divisions among EU members with Poland and Greece both threatening to refuse to sign a formal declaration unless given concessions on pet issues.

And looming over the summit will be Theresa May’s decision to trigger Article 50 next week and begin formal talks to secede from the Union – a reality reflected in the fact that Mrs May will be absent from Saturday’s line-up of leaders.