France has been requesting assistance in west Africa for two years

Britain is in talks to join a French-led operation against Islamist militants in west Africa as part of a desire for closer military ties between the two countries before Brexit.

Theresa May and President Macron are expected to announce the move at a Franco-British summit next week in London. The British contribution looks set to involve military helicopters or surveillance aircraft rather than sending combat troops.

“We are looking at rotary support or Istar [Intelligence, surveillance, target acquisition, reconnaissance],” a Whitehall source said. “The effort is counterterrorism, to counter organised crime and to help re-establish state authority.” The operation across Africa’s Sahel region is also regarded as a way to help stem the flow of migrants crossing into Libya and then Europe.

In a reciprocal