Eighteen months ago, Tom Harvey retired. Then this year he changed his mind and unretired. He is far from alone. In the UK, according to research in Aging & Society, 25 per cent of retirees return to work, about half of these within five years of retirement.

It defined unretirement as "reporting being retired and subsequently recommencing paid employment, or beginning full-time work following partial retirement (working fewer than 30 hours per week)". A 2010 study found that rates were similar in the US.