Tim Willetts, who oversees head recruitment for the south London borough, said: “It looked as if it would be an issue in the coming years. So a few years ago we got together with outside agencies, including universities, to establish a training programme for deputy heads.”

Under the scheme, deputies attend a series of seminars and share their experiences. The result is that in the past two years, between two- thirds and three-quarters of new heads in Wandsworth have come from the ranks of the borough’s deputy heads.

Seminar subjects include personalised learning, self-evaluation and assessment for learning. Every year a residential conference is held for all deputy heads.

A similar training programme has been set up for “middle leaders”, such as heads of department or subject co-ordinators, focusing on the skills they will need to move into leadership roles.

“We are trying to make sure our future heads feel they are equipped with as rich a set of research findings from the outside as possible,” Mr Willetts said. “In doing so we are successfully getting across the idea that headship in Wandsworth is a positive experience.”

Johnette Barrett Waite, head of Sellincourt primary, Tooting, is a beneficiary of the Wandsworth approach. A former educational psychologist, she was already considering becoming a head when she took on a deputy head post in the borough.

But it was the excellent training and mentoring scheme for newly-qualified heads that crystallised her ambition and convinced her to stay in Wandsworth.

“It made me feel I would be valued and looked after and supported if I became a head here,” she said.