The two leaders are set to confirm details of a strengthened defense relationship at a summit Thursday. An agreement on tackling unauthorized migration may also be announced.

Britain and France will join together to use nuclear weapons against any “extreme threats” towards Europe, Sir Keir Starmer and Emmanuel Macron have declared. A newly-signed declaration by the leaders will state that the two countries’ nuclear deterrents are independent but can be co-ordinated in a joint attack on Europe’s enemies.

The French president and the PM are co-hosting the Franco-British Summit on the final day of Macron's state visit to the UK.