The band's mainman was forced to retire earlier this year as his condition deteriorated. Latest album Rock Or Bust, released on Monday, is their first without him.

Angus Young recently revealed that his brother had begun experiencing problems before they decided to embark on the three-year tour in 2008, which became the fourth biggest-grossing of all time. At times he had to relearn his own riffs.

Now Johnson tells the Guardian: "It was tough. But you couldn't say anything or do anything because it would have been like giving pity. You had to treat it like a normal day - so we did."