By Michael Crick
Presenter, When The Power's Switched Off, BBC Radio 4
About ten weeks from now, around the middle of Wimbledon fortnight, Tony Blair will travel to Buckingham Palace and formally hand in his resignation as the Queen's tenth prime minister.
He will certainly enjoy his freedom, now the burdens and pressures have suddenly vanished.
Yet leaving Number Ten can be a terribly difficult process, even if - like Tony Blair - you have long planned for it.
John Major said it took him about a year to recover physically. Margaret Thatcher's friends say she has never really recovered psychologically from the blow.
While Ted Heath was so unprepared for being turfed out of Downing Street in 1974 that he didn't even have anywhere else to live - and had to borrow a flat from his parliamentary aide Tim Kitson.
But having shed the burdens and responsibilities of the premiership, what next?
First, there is the question of whether to stay in politics.
John Major, remarkably, seems pretty much to have left politics altogether, confining his interventions to the odd appearance on the Today programme, and even then it is often to talk about cricket.
Should you stay in the Commons or not?
Tony Blair is expected to quit his seat at the next election, but Winston Churchill remained an MP for almost another ten years.
John Major had more time to pursue his love of cricket
Ted Heath spent much longer in the Commons after he was PM (27 years) than he had before (20 years).
Some former prime ministers even go on to serve their successors.
Arthur Balfour spent eleven years in Cabinet under various successors, while Sir Alec Douglas Home was Ted Heath's Foreign Secretary.
Heath wanted to do the same job for Margaret Thatcher.
She offered him the post of ambassador to Washington instead, which he thought was an insult.
Then there is the question of whether to go to the Lords.
It is surprising how many modern prime ministers do not bother with a peerage - Churchill, for example, Heath and Major.
Harold Macmillan waited twenty years before joining the Lords, which he called "the morgue".
Nor, we are told, will Tony Blair bother with the upper house.
There is also the possibility of roaming overseas.
Tony Blair, like his friend Bill Clinton, will probably want to do something on the international stage, with the Middle East likely to be his main area of interest, especially following his success in the Northern Ireland peace process.
But given Blair's unpopularity in much of the world, and his association with George Bush, America and the Iraq War, it is hard to see him getting a big job in the EU, the UN, or even NATO.
Surprisingly, no British PM has ever been a European Commissioner.
But the biggest political question is how much you keep your mouth shut.
Ted Heath regularly embarrassed and annoyed his Tory successors.
So too did Margaret Thatcher, but Jim Callaghan and John Major have been pretty loyal.
Will Tony Blair be able to resist speaking out, even very gently, against Gordon Brown, the man expected to succeed him?
A tricky problem when you know every utterance will be scrutinised for the slightest hint of criticism.
Then there are the memoirs.
These days prime ministerial autobiographies involve teams of researchers, and ex-PMs are given a small room inside the Cabinet Office where they are allowed to order up official government papers, just to make sure they don't get let down by their memories.
And the memoirs, of course, aren't just a chance to make money - often many millions these days - but are the first step in establishing your place in history, putting the record straight and burnishing your reputation.
But two bits of advice to Tony Blair from those we have interviewed for this programme.
Clement Attlee left barely £7,000 in his will
First, get your book out quickly. Ted Heath waited more than 25 years to publish his memoirs, by which time they no longer really mattered.
Second, make sure you credit everyone who deserves it. In John Major's book, Edwina Currie's name was accidentally cut out in the last-minute editing process.
She was reportedly so angry not to see her name mentioned even once that it prompted her famous decision to reveal details of her affair with Major in her own subsequent diaries.
And if you do not make enough money from the memoirs, there are numerous other opportunities to make money, though the prime minister this week refused to answer when I asked him this week whether he planned to "cash in".
Bill Clinton is reckoned to have made $40m in the six years since leaving the White House, and Tony Blair can expect to make perhaps $50,000 - $100,000 a throw on the lucrative US lecture circuit.
And there are directorships and consultancies such as John Major's well-paid work for the global private equity firm the Carlyle Group.
Tony Blair will find it is all a far cry from his Labour predecessors.
Clement Attlee left barely £7,000 in his will, while Harold Wilson and Jim Callaghan both enjoyed fairly modest lifestyles after they stepped down.
Even without memoirs and outside work you get a tidy sum these days from two separate state pensions - you get half your salary as PM from the day you step down until the day you retire and then, at 65, a second very generous pension for your time as an MP.
Tony Blair will be only 54 when he leaves Downing Street in late June or early July.
Assuming good health, that could leave him with thirty or forty years to enjoy his post-premiership.
The possibilities are endless.
When The Power's Switched Off will be broadcast on BBC Radio 4 on Saturday 21 April at 1030 BST. You can listen to it online by clicking on the link under the photograph of Tony Blair [top].