Orlin Roussev, 47, who admitted conspiracy to spy under the Official Secrets Act last year, was the linchpin of a spy ring made up of Vanya Gaberova, Tihomir Ivanchev, Katrin Ivanova, Biser Dzhambazov and Ivan Stoyanov.
The six Bulgarian nationals will be sentenced for the same offence later this year at the Old Bailey.
Gaberova, 30, Ivanchev, 39, and Ivanova, 33, all denied the offence but were convicted after a three-month trial.
Part of the operation reportedly involved using prostitutes to infiltrate Merville Barracks, with Roussev said to have come up with the idea after allegations arose of “orgies” being held among members of the 3 Para of 16 Air Assault Brigade in June 2022.
The Sun reported at the time a prostitute had visited the base up to 31 times, with soldiers later told to take STD tests.
The Mail has reported Roussev’s plan to use prostitutes to gather information was ready to go, only for the operation to be stopped by the British authorities when armed police raided his Great Yarmouth guesthouse in February 2023.
Had Roussev succeeded in sending prostitutes into the barracks, it would have represented a major security breach and risked further embarrassment for the Parachute Regiment.
His arrest led to thousands of items of evidence being seized from his Yarmouth address before further raids were carried out in Euston as police uncovered the scale of the operation.
Roussev had tried to deceive police when he was arrested, telling them they were searching the wrong address, but the devices seized showed thousands of messages he had exchanged with accomplices.
The Metropolitan Police’s Dom Murphy, who is the force’s counter terrorism lead, said the spying was “on an almost industrial scale”.
He said: “It felt like something you would expect to read in a spy novel. This is not something we see very often.”
The Ministry of Defence declined to comment on Roussev’s attempts to infiltrate the barracks as the action was never carried out.
