The first woman to join an infantry regiment has quit after just two weeks training.
The recruit dropped out of an 18-week course after reportedly falling behind her male counterparts on endurance marches and failing other physical tests at a training base in Suffolk.
The woman, who is understood to have resigned, had been serving as a steward in the RAF and was seeking to transfer into the RAF Regiment.
The 2,000-strong unit is deployed to protect bases and airfields across the world and has sustained casualties in Afghanistan.
It also provides troops to support Special Forces operations.
Last September the RAF became the first military service to open up all roles to men and women.
Females could apply to join the RAF’s ground-fighting force after the Government lifted the ban on them serving in close combat roles.
In 2016, then prime minister David Cameron said it was essential the make-up of the Armed Forces reflected society.
The woman’s resignation is a blow to officials who are determined to integrate women into fighting units in the Army, Royal Marines and RAF.