Now, 35 years after the murder of a British intelligence source, Britain faces calls for a public inquiry for its role in the capture, detainment and later execution of a Guatemalan soldier who escaped a massacre and fled to neighbouring Belize. Our sources suggest that the man was actually an agent, loyal to the British intelligence services, and that he was given over to the notorious Kaibiles special forces unit to avoid causing embarrassment to President Reagan, who spoke of Rios Montt as ‘a man of integrity’.

In 1983, Britain had a garrison of 1,500 soldiers stationed along the Guatemalan border, which had been a UK colony until a recent independence vote. Politicians in Westminster and the public believed that the British Army was there to prevent Guatemala invading Belize, which it has long claimed as its own.

We can now reveal that Prime Minister Margaret Thatcher regularly allowed her troops to help the brutal Guatemalan military dictatorship eliminate its internal opponents. Senior officers within the British forces routinely dined with figures from the Guatemalan military, including the officers from the infamous Kaibiles special forces unit.

A source in Belize has now come forward with astonishing claims about the execution of a man named Alejandro Ruano, whose mutilated body was delivered to his family’s door a week after the British authorities handed him to the Kaibiles – along with a taped recording of his claims about the massacres occurring among the indigenous Mayan population.

Alejandro’s younger brother, Diego, said: ‘He was the bravest of all of us. We knew he was working for the British intelligence service. He risked life and limb to feed information to his handler about what the Kaibiles were doing. He was part of a network that nobody has ever admitted to – a unit run by a few half-decent people who wanted to undo the damage caused by their governments.