Is this déjà vu all over again? Among the activist investors currently rattling the cages of US companies are some faces who have been around this block before. Step forward Carl Icahn and Kirk Kerkorian.

Quite why we are seeing such a flurry of activity now is unclear. It may be the confluence of a number of factors: the huge amount of cash on balance sheets, the pressure on hedge fund returns, a more responsive corporate governance culture. For whatever reason, activism is back in fashion.