On Saturday, 2,000 people marched to the Russian embassy in west London , i n support of Ukraine ahead of the anniversary of the invasion.

According to a Downing Street spokesperson the prime minister also said “Ukraine must be at the heart of any negotiations to end the war” and it could be sure of “the UK’s commitment to securing a just and enduring peace to bring an end to Russia’s illegal war”.

Giving details about the phone call, Downing Street said Sir Keir and Zelensky “agreed that this was a significant moment for the future of Ukraine and European security at large”.

Sir Keir also told Zelensky “that safeguarding Ukraine’s sovereignty was essential to deter future aggression from Russia”.

The prime minister added “he would be progressing these important discussions in the coming days and weeks, including with Trump whilst visiting Washington DC next week”.

Zelensky said he had a productive talk with Sir Keir, with the pair coordinating “our military cooperation, joint steps, and engagements for the coming week, which will be very active”.

In a post on X, he wrote: “The UK and its people are among Ukraine’s biggest supporters, and we deeply appreciate this.”

Writing in the Sun, external Sir Keir said Trump was right that European nations must take greater responsibility for their security and increase defence spending.

“We have talked about this for long enough. Now it is time for action.

“President Trump is also right to grasp the nettle and see if a good peace deal is on the table.

“Every time I have spoken with him, I am struck by his commitment to peace,” he wrote.

Sir Keir also said Ukraine must have a voice in negotiations and needed strong security guarantees, adding: “I believe America must be part of that guarantee.”