Heidi Gardner knows how to get law firms to pay attention when she tells them collaboration – not exorbitant rewards to rainmakers and an eat-what-you-kill environment – is the key to long-term success and profitability: by using hard data.

Research by the ex-McKinsey consultant and distinguished fellow at Harvard Law School's legal profession centre shows partners can earn four times as much revenue when they involve more colleagues, and there is a "powerful" correlation between profit and the number of partners collaborating on projects.