Why are we asking this now?
Television viewers have a treat in store. A new drama is in preparation, about privately educated and very self-confident young men showing off in an elite university in bygone years. It will look like a dramatisation of an Evelyn Waugh, but actually it will be a drama documentary about the two men whose rivalry will be a major element in Conservative politics for many more years. Despite their shared past, David Cameron and Boris Johnson are not soul mates. Their relations are tense – even, it is suggested, at breaking point.
Didn't Cameron hold Johnson's arm up in triumph, after the Mayoral victory?
It was a great symbolic victory for Cameron's Conservatives when London, which has been a Labour city since 1981, voted a Conservative Mayor into office. But while Cameron very much wanted the Mayor to be a Conservative, it did not necessarily follow that he wanted it to be Boris Johnson. The original Tory choice was the personable Nicholas Boles, but Cameron was not sure that he could win and sounded out all sorts of people, including Sir John Major, and even approached the Liberal Democrat leader Menzies Campbell about the possibility of running Greg Dyke as their joint candidate. The one person he did not ask was Boris Johnson. When Mr Boles had to pull out for health reasons, Cameron was left with no candidate, but still could not bring himself to approach Johnson in person, getting a go-between to sound him out.
But haven't they known each other for ever?
In autumn 1979, when 12-year-old David Cameron arrived as a boarder at Eton, Boris Johnson was 15. With his blond hair and extroverted ways, Boris was not the sort of person to pass unnoticed, even as teenager, so Cameron must have been aware of him from a very young age. It will have taken Johnson longer to be aware of his younger, quieter and seemingly less talented fellow pupil. Each was certainly aware of the other when they were at Oxford University in 1985. Both were members of the elite, rowdy Bullingham Club. On the night police were called because of the damage club members had done to a restaurant, Cameron had reportedly missed the fun by going to bed early, while Johnson ran fast enough to avoid arrest.
When did Cameron overtake his school chum?
Cameron and Johnson became MPs on the same day in June 2001, after a general election, each with a safe seat. Johnson was then far better known than Cameron. He was editor of The Spectator, chief commentator for The Daily Telegraph and had made an unforgettable appearance on Have I Got News For You. Cameron was best known as the young adviser standing in the background in September 1992 as Norman Lamont emerged from the Treasury to announce that it was Black Wednesday. But Cameron cultivated much better relations with the party leader, Michael Howard. Howard sacked Johnson from the front bench because of his torrid private life, and raised Cameron to the key position of shadow Education Secretary.
Were they not political allies all this time?
When David Cameron decided to run for the party leadership in 2005, Boris Johnson threw the weight of The Spectator behind his campaign, and might have expected a place in Cameron's shadow Cabinet in return, but all he was offered was the second-rank post of shadow higher education minister. A worse snub was that in 2007, Cameron promoted three MPs to his shadow Cabinet who had been MPs since only 2005, but left the more experienced Johnson in his old job.
What are they arguing about now?
Johnson is a keen supporter of Crossrail, a planned new rail link traversing London east to west, but Cameron and his shadow Chancellor, George Osborne, are looking for ways to cut public spending and see this as a possible saving. They are also not very impressed by Johnson's highly controversial suggestion of building a new airport on marshland in Kent, to relieve Heathrow, and do not support his call for more power to be devolved to the Mayor's office.
Is it just personal rivalry driving these quarrels?
Boris Johnson and David Cameron are being pulled in different directions. The Conservative leader wants to win a general election, which means trying to get across the message that the Conservative Party is not exclusively the party for the comfortably off. Johnson has to consider the Londoners who voted him into office, who by national standards are well off. So when Cameron talks of a "broken society", Johnson calls it "piffle". When Labour introduces a 50p tax rate for the highly paid, Johnson wanted the Tories to promise to scrap it, because there are a lot of highly paid people in London, including Johnson himself, who dismissed the £250,000 a year he receives from journalism, on top his £140,000 salary, as "chickenfeed". Cameron is not prepared to make that promise.
So how well is Johnson doing?
After almost 15 months in office, Boris Johnson is still popular. If he had to stand for re-election today, he would almost certainly win. That has a lot to do with his highly recognisable personality. There are perhaps only two Conservatives most people can instantly identify from their first names, one called Margaret, and the other called Boris. His personality will boost the Conservative vote in the general election, in London at least.
What changes has he made in London?
Johnson hasn't produced a single change that would match Ken Livingstone's congestion charge for its impact on life in the city, but he has brought in some smaller reforms, such as banning alcohol on buses and tubes. He has honoured a pledge to slowly withdraw bendy buses (the first are coming off London's streets at the moment) and has unleashed a competition to design a Routemaster fit for the 21st century.
He has also put more police on the streets and on public transport, having made knife crime in particular a pillar of his election campaign, but made a public U-turn on tall buildings, which critics suggested was proof of his being enthralled by big money. He has taken up where Livingstone left off in championing the 2012 Olympic Games.
Is he a tough boss?
Johnson showed that he can play hard ball when he sacked the Metropolitan Police Commissioner, Sir Ian Blair, and was quick to accept the resignation of the chief of counterterrorism, Bob Quick, who accidentally held up sensitive papers in front of cameras. He has not been good at selecting deputy mayors: three have had to resign. Personnel additions have been shrewd, however. Guto Harri, the former BBC correspondent and a friend of Johnson's from his Oxford days, has become his chief spin doctor, while Anthony Browne, a former journalist, is now his director of Policy. They have run a disciplined operation between them.
Can Johnson and Cameron overcome the differences between them?
* They will put aside their differences for the sake of the Tory Party.
* Johnson will seek to carry on being Mayor until Cameron departs.
* Tory grassroots will not support an attempted coup for fear of stoking civil war. They remember well the baleful consequences of Michael Heseltine's unchecked ambitions.
* Johnson's claims not to covet the job of prime minister ring hollow.
* The pair have never mixed socially and are very different characters, despite their shared background.
* Johnson's popularity, with both Tory members and the public, could encourage his supporters to force prime minister Cameron out.