Lucy Heller does not usually do media interviews. Over her 22 years at Ark Schools - the 39-school multi-academy trust and charity with its fingerprints on a plethora of notable education organisations - there has been plenty she has wanted to talk about, but she’s tended to air her views in private: to ministers, to advisers and civil servants, to policy groups, to trusted peers, and to the hedge-fund backers of her organisation. It’s proven an effective strategy for wielding influence.