UK and Germany sign the Treaty of Kensington: what it is and what it provides for

Furthermore, the two countries will jointly develop a new long-range missile system and hold high-level meetings every year to 'coordinate foreign, security, and defence policy' to jointly counter foreign interference and threats from hostile states. In particular, the defences of European regions bordering Russia will be strengthened.

The two leaders reiterated their support for Ukraine and thanked US President Donald Trump for his willingness to supply arms to Ukraine, which according to Starmer demonstrates the positive effects of cooperation between Britain, France and Germany.

For Starmer, this is another important step in his strategy of progressive rapprochement with Europe after the Brexit tear. The Prime Minister has paid particular attention to mending relations with France and Germany and has just hosted French President Emmanuel Macron for a state visit, during which the only two European countries with atomic weapons initiated unprecedented cooperation on nuclear power.

The signing of the similarly unprecedented treaty with Germany raised some concerns in NATO, but both London and Berlin emphasised that the bilateral agreement is a pragmatic arrangement to re-establish cooperation interrupted by Brexit and that it is in no way intended to replace NATO or prevent future defence arrangements between the EU and the UK.

The treaty is "a historic document that demonstrates our ambitions for the future," Starmer said. In addition to defence cooperation, the agreements provide for close cooperation in the fight against terrorism, organised crime and illegal immigration.

Many of the tens of thousands of migrants who cross the English Channel each year to enter England illegally pass through Germany. A new law due to come into force by the end of the year will give German police more powers to investigate human trafficking gangs, search warehouses and confiscate the boats and dinghies used for the crossing. Aiding human traffickers will become a crime.

"Our friendship treaty represents freedom, security and prosperity, and will bring our younger generations closer together," Merz said. The agreement also provides for facilitations for youth mobility and children on school trips will not need visas.