Costs lawyer Jim Diamond (pictured) argues major law firms have over-charged their clients by £5bn in the last five years

Over-charging by major City law firms could be as high as £5bn over the last five years. I estimate that the flawed system that lawyers continue to use to produce bills has led to charges that are, on average, 5%-10% higher than they should have been across the board. And I believe that when the fundamentally flawed system finally unravels, it will make the MPs expenses scandal look like children taken a few loose sweets from a corner shop.