Calls for Prince William to leapfrog his dad to the throne have died down of late, but here's a new interesting theoretical royal question of the day - could Prince William sideline his dad and become head of the Commonwealth when his grandmother dies?Unlike the throne, the Commonwealth role does not pass automatically to the Prince of Wales but is decided on by the 53 Commonwealth leaders.Daily Mail diarist Sebastian Shakespeare suggests today that after William's 'triumphant' tour of Australasia - and Charles's allegedly less than stellar performance at the Commonwealth's heads of government meeting in Sri Lanka last year - there is a welling of support for William to bypass his dad.Realistically, the chances of this happening are next to nil - it would cause huge controversy if the Commonwealth role was decoupled from the monarch - but, hey, its fun to speculate sometimes.