It has been a significant week for David Cameron, the Conservative leader. Alistair Darling finally admitted in the Budget what a terrible state the public finances are in. Even on the Chancellor's optimistic forecasts, it would take a public spending freeze lasting 21 years to restore the national debt to the sustainable level once enshrined in Gordon Brown's golden rule (remember that?), according to the Institute for Fiscal Studies. Borrowing may well be the right policy for the moment, but it comes at the price of fiscal pain for years, if not decades, to come. Meanwhile, the Labour Party's reputation for economic competence has been devastated.
For that reason, we could look back on last week as the moment it became certain that Mr Cameron would become prime minister. He has shown some maturity in preparing people for lower public spending in the new "politics of austerity". But he has avoided specifics – and the word "cut" – a tactic that will come under pressure over the coming year.
The voters also want to know more about the kind of man that Mr Cameron is. In his three and a half years as Conservative leader, he has successfully presented himself as a different kind of Tory; yet some doubts remain about the ideological journey of the man who wrote Michael Howard's manifesto.
What, then, to make of our report today that the young Mr Cameron went on a trip to apartheid South Africa paid for by corporate lobbyists against sanctions? Let us be clear at the outset that it does not tell us anything definitive. The Conservative Party under Margaret Thatcher was opposed to apartheid, but did not agree with sanctions as a means to bring about change, and would claim vindication in the eventual outcome. Mr Cameron was a 23-year-old desk officer in the Conservative Research Department.
Yet it was not a trip that anyone passionately opposed to apartheid would have joined. By going, Mr Cameron implied an indulgence of the racist white government that was too much, officially, for the Thatcher government. Civil servants and special advisers were told not to go, and many MPs turned down the trips. On the other hand, it might have seemed rather priggish for a young man in that milieu to have said no to an expenses-paid trip – and it was a chance to see the country for himself. Furthermore, Mr Cameron's opposition to apartheid may not have been absolutist or demonstrative, but it was well informed. He had worked for Tim Rathbone, his godfather, a moderate Conservative MP who campaigned against apartheid but who was also opposed to sanctions.
Mr Cameron was a self-confident young man, and it was one of the marks of his self-confidence that he was able to accept later that the Conservative Party had been wrong about South Africa. After he became leader, he went there to meet Nelson Mandela and to say: "The mistakes my party made in the past with respect to relations with the African National Congress and sanctions on South Africa make it all the more important to listen now."
That was absolutely the right posture for him to adopt – so much so that it almost suggests calculation. Indeed, it would not be too cynical to suggest that one of Mr Cameron's motives in seeking an audience with Mr Mandela, who was in prison at the time of Mr Cameron's earlier visit, would have been to inoculate himself against the eventual revelation of his previous trip.
It is, though, what Mr Cameron says and does now that matters most. As this newspaper asked when James Hanning and Francis Elliott discovered for the first edition of their biography that he smoked cannabis at Eton when he was 15: who has not done foolish things when they were young?
His association with lobbyists who were, in effect, apologists for apartheid reminds us that his political formation was the conventional Conservatism of a privileged upbringing. It sits more easily with the image of Eton, the Bullingdon Club and the inside track of special adviserdom. More easily than with the image of the modernising leader that got a Tory conference to applaud gay marriage; that admitted the party got it wrong over South Africa; that is now opposed in principle to the extension of academic selection in state schools; that seeks to extend the ethnic diversity of its parliamentary candidates.
The revelation emphasises Mr Cameron's break with the assumptions of his early political formation. We do not believe that Mr Cameron's trip many years ago is an ineradicable mark against his name. It is not a hanging offence. But one wonders about the type of person that would do it, and how it squares with what he claims to be now. Mr Cameron still needs to allay the doubts that linger in many voters' minds about whether he and his party have really changed.