The United Nations World Food Programme has opened the door for dozens of ships trapped at Black Sea ports by the Ukraine conflict to make their escape.

War risk underwriters breathed a collective sigh of relief as 13 out of around 50 foreign-flag vessels caught up in the conflict so far have managed to sail free through a UN-backed safe maritime corridor.

If all the ships had remained caught at ports until February next year, the war-risk market could have faced claims up to $900m — based on current valuations — for total loss, under blocking and trapping clauses.