Sir Keir Starmer announced on Sunday that the UK and France were assembling a “coalition of the willing” to enforce any peace deal for Ukraine.

The Prime Minister revealed a “number of countries” had agreed to join the initiative at a summit of 19 international leaders in London.

Together with Ukraine, the European alliance will devise an alternative peace plan to the one being cooked up by Donald Trump’s administration in Washington before deploying a combined force to guarantee the settlement.

Sir Keir and Emmanuel Macron, France’s president, will work on the plan before presenting it to Mr Trump, who has already opened his negotiations with Russia’s Vladimir Putin.

European leaders have been scrambling to respond to those talks to ensure they have a seat at the negotiating table.

Partial one-month ceasefire

Late on Sunday, Mr Macron said France and Britain are proposing a partial one-month truce between Russia and Ukraine that would cover air, sea and energy infrastructure attacks.

Under the Franco-British proposal, European ground troops would only be deployed to Ukraine in a second phase, Mr Macron said.

Whatever deal is hammered out, the White House expects Europe to take responsibility for Ukraine’s post-war security.

Britain and France, in principle, have agreed that they will have to carry the bulk of that burden to keep Mr Trump on Ukraine’s side.

What is the coalition of the willing?

The security guarantees offered to Kyiv will have to be sufficient to deter Putin from breaking any ceasefire arrangement.

British and French officials believe this starts with continuing to build up Ukraine’s armed forces to create an effective deterrence.

Boris Johnson, although not involved in the process, describes this as turning Ukraine into a “steel-quilled porcupine”, which Putin would think twice about taking a further bite from.

Ursula von der Leyen, the European Commission’s president, used the same language, insisting Ukraine should be made “indigestible” to invaders.