Angela Merkel had heard enough. After a ten-minute presentation by Theresa May and a discussion in which she had used the time-worn phrase “Brexit means Brexit”, the German Chancellor was running out of patience.

“What else do you want?” the exasperated Mrs Merkel demanded of Mrs May, after the Prime Minister had failed to explain what it was she actually expected her counterparts to offer.

For Mrs May, the inquisition was a new experience; at previous summits she has made her pitch to a silent audience, then left the room so they could all dissect her pleas behind her back.

And, according to sources who witnessed Thursday night’s exchange, it was a deeply uncomfortable moment for Mrs May.

“She…