Last September, a Challenger 2 was destroyed by enemy fire in southern Ukraine when Ukrainian forces were bogged down by Moscow’s defences.

The Ministry of Defence has never placed restrictions on the use of conventional British weapons on Russian soil, as long as they are used against targets in accordance with international law. However, Storm Shadow cruise missiles have been restricted to targets on Ukraine’s sovereign soil and the occupied peninsula of Crimea.

Classified US intelligence documents leaked shortly after their delivery to Ukraine said the Challengers were assigned to Kyiv’s 82nd brigade. Elements of the brigade were part of the initial thrust into Russia, made up of four elite brigades trained and equipped by Nato.

A now-deleted photograph shared by the 82nd Air Assault Brigade, elements of which are fighting on Russian soil, showed the British-donated tank in the background.

Ukraine has captured more than 1,000 square kilometres of the Kursk region since its forces launched the surprise cross-border raid into the region early last week.

Kyiv’s has made use of US-supplied Stryker armoured fighting vehicles, German-made Marder tanks, mine-clearing machines and tank transporters, and at least one French armoured personnel carrier.