Legal & General Investment Management, Britain’s biggest fund manager, is to mount a global campaign for one of the oldest and most basic rules of UK corporate governance — almost 30 years on from its origin.

The principle that the roles of company chief executive and chair of the board should not be held by the same person — because chairs are supposed to double-check a chief executive’s decisions — dates from the forerunner to the UK’s original corporate governance code, known as the Cadbury Report and established in 1992.