He singled out Ferguson's remarkable ability to continually reinvent his teams as his greatest managerial strength.
"Alex is a genius," said Charlton, a star of Sir Matt Busby's legendary line-ups of the 50s and 60s.
"The number of times when you think he's gone a bridge too far, he has succeeded. Even when people thought players were too young, he didn't. Tom Cleverley as come in this season, and he and all the young lads have started to blossom. Alex just talks to them and they listen."