Johnson signed the agreement at around 1pm, following a meeting with Magdalena Andersson at her official country residence in Harpsund, 100km west of Stockholm. He is now due to travel to Finland to sign a similar deal.  

According to the text of the so-called “Political Declaration of Solidarity,” each country commits to come to the other’s aid in the even of an attack. 

“Should either country suffer a disaster or an attack, the United Kingdom and Sweden will, upon request from the affected country, assist each other in a variety of ways, which may include military means,” the text reads.

But it adds a caveat. “Such an intensified cooperation will remain fully in line in with each country’s security and defence policy and is designed to complement not replace existing European and Euro-Atlantic cooperation.” 

According to a press release from the UK government, as part of the deal the UK will also offer to send ships, troops and fighter jets to the Nordic region. 

“As part of increased defence cooperation with Sweden and Finland, the Prime Minister will offer to increase deployments to the region, including with Royal Air Force, British Army and Royal Navy assets and personnel,” it reads. 

At a press conference after the deal was signed, Andersson said that under the deal UK had undertaken to provide “military resources” in the event of an attack on Sweden, even if Sweden decided not to apply for Nato membership.

“The prime minister and I have agreed…if either country should suffer a disaster or an attack, the United Kingdom and Sweden will assist each other in a variety of ways,” Andersson said. “The support will be given on request from the affected country, and may include military resources.”

“What we are saying, emphatically, is that in the event of a disaster or the event of an attack upon Sweden, then the UK would come to the assistance of Sweden with whatever Sweden requested,” Johnson said. 

The deal would also deepen defence cooperation more broadly, he said. 

“This mutual security assurances declaration is an agreement which brings our countries even closer together, it will allow us to share more intelligence, bolster our military exercises and further our joint development of technology.” 

Johnson alluded to the decision Sweden is soon to make on Nato, which looks likely to bring an end to the country’s long history of neutrality and non-alignment, and which is likely to antagonise Russia, which has long complained of Nato’s expansion. 

“The war in Ukraine is forcing us all to make difficult decisions, but sovereign nations must be free to make those decisions without fear or influence, or threat of retaliation,” he said. 

“It’s also an important step forward. This is an agreement on which we, together, intend to build, whether it’s in sharing intelligence or working together to combat cyberattacks, whether it’s working together in defence procurement, whether it’s doing joint exercises together, Sweden and the UK intend to do much more together,” he said.

In comments to Swedish newswire TT, Malena Britz, a researcher at the Swedish Defence University, pointed out the similarities between the agreement and EU security agreements outlined in article 42.7 of the Lisbon treaty.

“You could say that we are regaining the support we had from the Brits before they left the EU,” she said.

“They discussed supporting with all possible resources, including militarily, and that’s pretty much exactly what is covered in current EU leglislation.”

Article 42.7 has been criticised for not including any guarantees of military support.

Britz told TT that the new agreement has not improved Sweden’s military preparedness, but that the fact that there is now a political agreement in place will make it easier to use any military tools required if this becomes necessary in the future.

“To use the military tools you have within the framework of these commitments, you need political agreements,” she said.