… Often, particularly when dealing with a vain and ageing film star, courtesy may amount to little more than intelligent self-interest. Who wants to upset a good client, when all you have to do to keep her sweet is swallow an obvious reply? You can, after all, tell the truth and still be courteous – and circumspect. Take this reported exchange between Marlene Dietrich and an anonymous photographer.

“Your photographs are not so good any more,” she told him. “Eight years ago, you used to make me look wonderful.”

“Yes,” he replied, nodding sadly. “But I was much younger then.”…