According to this story in the Daily Telegraph, London the man who was in charge of jailing McCain when he was in the Vietnam war.
According to the story:
Tran Trong Duyet, the commandant of Hao Lo prison in Hanoi from 1968-73, recalls Mr McCain "as a typical child of a traditional military family. He was conservative and faithful to his country's policy of the Vietnam war".
"In a talk between men we shared many things about girls and love and so on," said Mr Duyet, who claims Mr McCain helped teach him English.
"I think John McCain is a very smart man."