Britain will send military helicopters to join a French campaign against Islamist extremists in Africa as London and Paris move to deepen cross-Channel defence ties, the Prime Minister is expected to announce later this week.

RAF Chinooks have been offered to transport French troops in discussions ahead of a Franco-British summit on the military, security, space research and immigration.

Talks at Sandhurst will see Theresa May and Emmanuel Macron agree closer cooperation on fighting al Qaeda linked militants “at source” in north Africa.

The French president on Tuesday also said he will demand Mrs May take more responsibility for the refugee crisis as he vowed there would be no return of the so-called "jungle" migrant camp in Calais.

Around 4,000 French troops are waging a cross-border counter-terrorism campaign throughout the southern Sahara, with forces deployed to back local governments in Mali, Mauritania, Niger, Chad and Burkina Faso.