In the run-up to Vladimir Putin’s assault on Ukraine, Moscow notified Turkey of its intention to send one of its most imposing warships, laden with cruise missiles, through the heart of Istanbul to join the impending onslaught.

But the Admiral Flota Kasatonov — and three other vessels that had been expected to traverse the Dardenelles and Bosphorus straits — did not make the journey over the weekend, as Russia had planned, two western officials told the FT.

On Monday, president Recep Tayyip Erdogan indicated that he would enact a clause in the 1936 Montreux Convention that allows Ankara to curb the passage of naval vessels belonging to warring parties. “We have the authority and we have decided to use it in a way that will prevent the crisis from escalating,” he said.