It is time to play the age old game, construct a cabinet. Gordon Brown will have considerable leeway. The only person forced upon him will be the Deputy Leader, whom he has promised to accomodate, presumably reasoning that anyone with the least chance of being elected is acceptable to him.
The Chancellor's job will be vacant, as will the post of Home Secretary. The Deputy PM, while undetermined, will certainly be someone new. Unless it is Harriet Harman (or, theoretically, John Cruddas, but it won't be), it will be someone already in the cabinet.
In addition to Blair, Prescott and Reid, whom we know are going, we can be reasonably confident that Lord Falconer, Tessa Jowell, and Patricia Hewitt will be fired. Jacqui Smith and Hazel Blears will not be kept in their current roles, but both may stay in the cabinet - indeed, in the case of Hazel Blears this is extremely probable. Margaret Beckett is quite likely to go, as are Ruth Kelly and Hilary Armstrong. So, without Brown having to be especially ruthless, around a third of cabinet will go. This includes all the top offices, except Leader of the House, being almost automatically vacated.
So who will be going up? Douglas Alexander, Des Browne and Alistair Darling are all Brownites likely to move up. Jack Straw will probably move to a departmental role. Hillary Benn, Alan Johnson, and David Miliband are well thought of and have, perhaps, earned promotion. Benn is especially likely to move up. Peter Hain may also earn a front rank post.
Harriet Harman and Nick Brown will return to the cabinet, and key Brown lieutenants Ed Balls and Ed Miliband will join them.
The key decision is this: who gets to pretend they are Chancellor. Brown, of course, will stay in control of the Treasury, but someone has to have the job in theory. No PM since Gladstone has appointed himself as Chancellor: though Lord Salisbury was Foreign Secretary and Winston Churchill was Secretary of War.
The most obvious candidates are Jack Straw, Alistair Darling, and Ed Balls. Balls is the one Brown most trusts, but he will probably have to earn his spurs in another role first. Straw has held both the other Great Offices of State, and while he was not distinguished in either, nor was he disastrous. Alistair Darling is the safest choice, but he is Scottish and (unlike Tony Blair) sits for a Scottish constituency and has a Scottish accent. Brown has, apparently, been advised that putting a fellow Scot in such a high profile job would be damaging to the government's image. Constitutionally, this is preposterous. The Chancellor is as much Chancellor of Scotland as he is of England - something which does not apply to Darling's current role (Trade & Industry) or his previous post as Transport Secretary. He could, apparently, be Home Secretary, another post with almost no English responsibilities, but not Chancellor. The retiring Home Secretary for England is, of course, Scottish, and has been Health Secretary for England in the past.
If Brown, by virtue of personally sitting for a Scottish seat, feels more vulnerable to the West Lothian Question than Blair has done, then Chancellor is actually a very good job for Alistair Darling, and Home Secretary is the one he should be kept out of at all costs. Leader of the Commons and Foreign Secretary are also perfectly appropriate, though Foreign Secretary is thought to have Hillary Benn's name on it.