US DIPLOMATS stationed at a shadowy spy base in rural Northamptonshire have immunity from prosecution under a secret agreement — even though they work more than 50 miles away from the US embassy in London, it has emerged.

The agreement, which stretches back a quarter century to 1994, has only come to light following a hit-and-run scandal involving the wife of a US diplomat from the base in Croughton.

Anne Sacoolas, 42, is alleged to have killed local teenager Harry Dunn when she drove out of the spy base on the wrong side of the road on August 27.

The fatal crash has left Mr Dunn’s family heartbroken and demanding justice.

Ms Sacoolas told Northamptonshire police that she held diplomatic immunity because of her husband’s job, and returned to the US soon after the accident.

The prime minister has come under intense pressure to raise the issue with the US authorities, and Boris Johnson claims he will now urge Washington to review diplomatic immunity in this case.

However, it is not publicly known which agreement grants US personnel at the Croughton base immunity from prosecution.

US forces operate from Croughton under a Status of Forces Agreement (Sofa) from the 1950s.

The Pentagon has similar Sofa deals with countries around the world, to maintain its sprawling network of foreign military bases.

In 2016, the Pentagon had to amend its Sofa agreement with Japan to reduce the number of personnel eligible for immunity.

The move followed outrage at the rape and murder of a 20-year-old woman in Okinawa by a US army contractor.