When French private equity firm PAI Partners and US firm Blackstone bought the maker of Hobnobs and Jaffa Cakes, United Biscuits, back in 2006, they decided to sweeten the deal.

The firms tacked a "shareholder agreement" on to the deal that said that United Biscuits would have to cough up £2 million in fees to its new owners each year plus a one-off £20 million in transaction fees. Over the eight years that United Biscuits was owned by Blackstone and PAI, it paid them around £34 million, all for the pleasure of being owned by private equity.