Tech billionaire Mike Cannon-Brookes has dramatically intervened in a bid to single-handedly foil AGL Energy’s proposed demerger, taking enough of an interest in the company to try to ensure that the plan collapses.

Mr Cannon-Brookes’ Galipea Partnership bought just shy of 11.3 per cent in AGL through derivatives trades after the market closed on Monday, with a view to voting all its holding against the demerger, which needs 75 per cent approval.