Two months ago, Sir Peter Spencer was chief executive of the Defence Procurement Agency, with responsibility for a £6.5bn budget, 4,700 staff and, to no small degree, the defence of the realm. "I bought new equipment for the three armed forces," he explains. "Eurofighters, submarines, tanks, helicopters and all the nuclear stuff."
Spencer is now running the charity Action for ME, which has 20 staff and a turnover of less than £1m.
In many ways, the two positions could hardly be more different. "The sheer volume of work I dealt with at the DPA was inevitably bigger because of the complexity and scale of the job," he says. "I spent 25 to 30 hours a week travelling, usually working in the back of a car on my laptop. It became my mobile office."
These days, Spencer's office is a modest room overlooking the back streets of Bristol, and he is probably less paranoid about where he leaves his laptop. But although his tasks have changed, the challenge remains the same.
"I'm more struck by the similarities of the two jobs than the differences," he says. "Leadership and management depend on your ability to communicate, not only with the people you work with, but also with your stakeholders and the people with whom you form alliances."
Spencer joined the Navy from school in 1965. At 59, this is his first job in the voluntary sector, although he was tempted to make the move in 2003 before applying for the top job at the Defence Procurement Agency.
He has never had ME, but remembers a rector who lived next door to him 15 years ago who did. "Nobody understood it, and his life fell apart," he says.
Many people still don't understand the debilitating condition, even though it affects 250,000 people in the UK. ME, or myalgic encephalomyelitis, can be triggered by a number of factors and as yet has no cure. Also known as chronic post-viral fatigue syndrome, it is often dismissed as an excuse for apathy. This month, the charity criticised Sunday Times columnist Rod Liddle for describing it as a "fashionable, camp affliction".
Partly because of the charity's lobbying, the Department of Health in the UK and the World Health Organisation have recognised ME as a serious medical condition. But GPs and employers have no consistent approach to dealing with it. Consequently, diagnosis and treatment are hit and miss. "It can still be treated as a psychological rather than a neurological condition," Spencer explains.
The charity is campaigning for a consistent approach and is directing its campaign missiles at the National Institute for Health and Clinical Excellence and the Department for Work and Pensions. It's also lobbying the Medical Research Council to fund research and is running an awareness campaign this year on men and ME, because males are less likely to admit they have the illness.
The charity, which was founded when an article on ME in a Sunday newspaper received 15,000 responses, celebrates its 20th birthday this year. But this is a new beginning. Besides its new leader, it has new heads of fundraising and of operations. "The first thing we are going to do is a self-assessment of where we are, without making a great bureaucratic deal about it," says Spencer.
He might be a latecomer to charities, but Spencer says he's in it for the long haul. "I'll be here as long as the trustees want me," he says. "If we're going to achieve a transformation, the charity doesn't want some smart Alec flash in the pan. I've got at least 10 years of my working life left. I'm not here to develop a career. I'm here to develop a charity."
2007: Chief executive, Action for ME
2003: Chief executive, Defence Procurement Agency
2000: Second sea lord and commander-in-chief naval home command, Royal
1965: Navy cadet