Ms May showed no hint of irony as she told a session on counter-terrorism at the Group of Seven (G7) summit in Taormina, Sicily, that they must do more to ensure those travelling to Syria and Iraq to join Isis are brought to justice.

“It is vital we do more to cooperate with our partners in the region to step up returns and prosecutions of foreign fighters,” she said.

“This means improving intelligence-sharing, evidence gathering and bolstering countries’ police and legal processes.”