The criminal mastermind behind the notorious Great Train Robbery in 1963 that hauled in almost $4 million has died at age 81 following recent health problems, Breaking Celebrity News is reporting.

Bruce Reynolds was described as the brains of the infamous gang of British thieves who pulled off one of the biggest heists in history when they targeted a Royal Mail train from Glasgow that carried letters, packages and huge quantities of cash, which would be worth $60,650,000 today.

The robbers forced the huge diesel-electric locomotive to stop in Buckinghamshire, England, in the early morning hours of Aug. 8, 1963 by tampering with a signal and making it show red, reported The Huffington Post UK. They then stormed the train by force and unloaded the money in just 25 minutes onto a truck at a nearby station.

Train driver Jack Mills was struck in the head by gang member James Hussey during the attack and died from related injuries seven years later, although it was widely believed until last year that it was Ronald "Buster" Edwards who had delivered the fatal blow.