British troops on a Ukraine peace mission will be 'allowed to fire back' if Russia attacks, ahead of rehearsals in Poland

Some 300 soldiers from the British Army's 7 Brigade are deploying to Poland for the Coalition of the Willing's first major exercise, simulating moving troops and supplies into Ukraine after a ceasefire. Western officials stress any force sent would not take part in offensive operations, only reassurance and rebuilding of Ukraine's army.

Thousands of European troops are taking part in the rehearsal, which was agreed at a Coalition of the Willing summit in July.

The drill covers logistics including food and fuel movement, testing how allied forces could one day sustain a peacekeeping presence on the ground.

Officials confirmed British troops are preparing to defend themselves if attacked, but would not fire first under the mission's rules of engagement.