Robbins while he was president of the Oxford Reform Club at university

To his allies and admirers, Oliver Robbins is the very model of a modern major mandarin whose cool devotion to duty is helping Britain achieve a smooth departure from the EU.

To his Eurosceptic critics Theresa May’s chief Brexit negotiator is the great betrayer, a pro-Brussels Machiavelli driving a Trojan horse into the heart of government and steering the prime minister inexorably towards a soft Brexit.

Now the more suspicious among them will really have something to chew on when they learn that Robbins, 42, was a pro-EU activist who fought for a federal Europe during his days at Oxford University two decades ago — and was such a sinuous operator that he was even dubbed “Sir Humphrey” — after the pompous civil servant in