Alex Ferguson, former manager of Manchester United, once offered this universal truth about how to behave towards a successor: "It is unfair . . . to try and retain the authority you once possessed. You have to let go and let the new man and the new regime do what they think is best."
Sir Alex was being rather disingenuous. After David Moyes took over from him in 2013, the legendary coach stayed on as a club director. TV cameras recorded his every frown as he watched Moyes's flailing efforts from the stands. Sir Alex wrote in his 2015 book that they were trying "to catch me acting like Statler or Waldorf, the two curmudgeons in The Muppets, who are always criticising what is happening on the stage". It may not have been a deliberate haunting, but it probably felt like that for Moyes. He was sacked after only 10 months.
The uneasy detente between Travis Kalanick and his successor as Uber's chief executive, Dara Khosrowshahi, reminded me of the Statler and Waldorf risk. Kalanick is still on the ride-hailing company's board. He has to watch as the new boss changes the team he built, overhauls the culture he created, and reverses the management style he notoriously modelled.
Kalanick's restraint is admirable, if self-interested. As founder, he has a large stake in Uber, which went public last week. The real test of his self-discipline will come if his successor steers Uber back into trouble.
The responsibility of chief executives who are paid employees, rather than company creators, is clearer. "The general [public company] rule should be that once you leave as CEO you really do leave," says Ian Cheshire, former chief executive of Kingfisher, the UK retail group. He made himself available to advise Véronique Laury after handing over to her in 2015, but had "perhaps three chats". "The last thing your successor needs is [the CEO's] ghost hanging around to act as the lightning rod for any disaffected opponents of change," he says.