He said: “There seems to be a great deal of scepticism about what this incursion is going to accomplish.”

Regardless, Mr Zelensky has made holding on to Ukraine’s Kursk salient central to his ‘Victory Plan’, which he presented to Sir Keir Starmer last week.

But Russian forces have accelerated their attacks along the front line in Donbas since Ukraine invaded Kursk, and on Tuesday pro-Russia officials in occupied Donetsk said that they had now captured two-thirds of Toretsk, a key front-line town with a pre-war population of 34,000 people.

In the northern section of the front line in east Ukraine, Ukrainian officials have also ordered the evacuation of civilians from the city of Kupyansk on the banks of the Oskil river because of Russian advances.

Oleg Sinegubov, the head of the Kharkiv region , said: “The military situation is deteriorating and we cannot ensure the heating season, the provision of electricity, and humanitarian assistance. The enemy is shelling critical infrastructure.”