BORIS Johnson said the UK “will not hesitate” to defend against any threat from “21st century tyrant” Vladimir Putin.

The Prime Minister was speaking after signinig a security agreement with Sweden today, and is expected to make a similar deal with Finland.

Mr Johnson said it was “a sad irony” that the security assurance declaration was signed days after marking VE Day, but was more important than ever under the “grim circumstances” following Russia’s invasion of Ukraine in February.

He said: “This week, many of us have been paying tribute to the brave men and women who secured victory and peace in Europe 77 years ago.

“So, it’s a sad irony that we’ve been forced to discuss how best to fortify our shared defences against the empty conceit of a 21st century tyrant.”

Speaking alongside Swedish counterpart Magdalena Andersson at her Harpsund country retreat, he added: “The many carcasses of Russian tanks that now litter the fields and streets of Ukraine, thanks to Swedish-developed and British-built NLaws (anti-tank weapons), certainly speak to how effective that co-operation can be.”

He added: “Most importantly, this is an agreement that enshrines the values that both Sweden and the UK hold dear, and which we will not hesitate to defend.”

Ms Andersson said she was “very happy” to sign the bilateral agreement.

The two leaders sat together on a terrace outside the country manor to sign the declaration before walking side-by-side through the gardens of the estate down to a jetty overlooking the lake, where they briefly went rowing.

The Prime Minister later boarded his flight to Finland, where he is expected to formalise a similar pact with the country’s president Sauli Niinisto during a whirlwind 24 hours.

Mr Johnson said the agreement meant the UK “would come to the other (country’s) assistance” upon request in the event of a crisis, including increasing Royal Air Force, British Army and Royal Navy personnel and assets.

It comes as both European countries consider the prospect of Nato membership in the face of Mr Putin’s ongoing military aggression.

The declarations build on claims made earlier in the month that the UK would always aid Finland if it were attacked by Russia, regardless of whether the country was a member of Nato.

Defence Secretary Ben Wallace said it was “inconceivable” that Britain would not help either Finland or Sweden if it were in crisis, even “without any big formal agreement”.

Mr Johnson held talks with Ms Andersson and Mr Niinisto in March as part of a meeting of the Joint Expeditionary Force nations, which includes Denmark, Estonia, Iceland, Latvia, Lithuania, the Netherlands and Norway.

After the meeting, Downing Street said the two leaders agreed that “Putin’s invasion had dramatically changed the landscape of European security”.

Finland shares a lengthy land border with Russia and is only about 250 miles from St Petersburg.