Only two years later, he was discharged as medically unfit for service.
Before signing up for a three-year stint as a sapper with the Royal Engineers, he had been a keen footballer - one of the first players to sign for Johnstone Burgh Football Club in his native Renfrewshire.
He says: 'I was a destroyed man at the age of 21.'
Two-thirds of his stomach has been removed; he suffers from partial limb paralysis; and he is pursuing a claim through the European courts blaming his exposure to the nuclear explosions for the fact that he and his wife have been unable to have children. 'I suffered severe skin disorder on Christmas Island, and internal haemorrhage when I got back to Otterburn barracks in Northumberland.'
For reasons that he does not understand these conditions have not been entered on his medical records. Mr McGinley, 55, is chairman of the British Nuclear Test Veterans Association, which is fighting to obtain compensation from the Ministry of Defence for those former servicemen who have fallen ill and for the families of those who have died, after witnessing the tests.
The Government has refused to meet such claims. He believes that, in the eyes of the Ministry of Defence, 'the servicemen were expendable'.
Mr McGinley said: 'I was standing on the beach at Port Camp. I had on a white cotton overall - nothing for the eyes or the rest of the body - and a jungle hat. We were approximately 11 miles downwind - the wind was blowing towards us from the explosion.' He witnessed a further four tests while he was stationed at Christmas Island.
Mr McGinley rejects official reassurances that a couple of kilometres of air would have screened the servicemen from harmful radiation. 'If these tests were so safe, why didn't we just blow it up off the coast of Cornwall? Why did we have to go to the Pacific to set them off?' he asks.