I cannot have been alone in noticing the peculiar way that was used to herald the moment that the about-to-be-president stepped into public view for his inauguration. "Barack H Obama," intoned the unseen voice, moments after the trumpet flourish.

We had heard full names ("William Jefferson Clinton") but that mysterious "H" was notable. It was known in advance that the new US president would be sworn in with the use of his full name, for reasons not political, probably legal, most of all, simply factual. The name of the 44th president of the United States is Barack Hussein Obama. That is a fact, and not one that should be, or ever should have been, open for abuse and misinterpretation.

Yet that odd "H" was a reminder, although presumably not intended, of just such attempts to conjure up prejudice and fear (a friend, in the run-up to the elections, suggested that we all should introduce ourselves with the middle name, loudly enunciated, HUSSEIN, as a protest against bigotry and innuendo).

It was also a reminder, if one was needed, of how deeply felt is the need among Obama's supporters and his detractors to assign an identity to him. Obama is president in an age and at a moment that his performance is assessed hour-by-hour, minute-by-minute. The assessment of his legacy began when he was barely a day in the job.

Most of all, everyone seems to want to decide who he actually is, in the sense of assigning him the identity of someone else.

Even after Obama was elected, his detractors continued to wail: "But we don't really know who this man is" (in some cases at least, that was code for, "he's really an Al-Qaeda mole" and other such right-wing conspiracy theory claptrap).

No, we know who he is. We do not yet know how good he will prove at being the president of the US. Adding to that, "president of the US especially in these times, with two wars, the greatest financial crisis since..." is redundant. Every president comes into office facing a particular set of circumstances; some circumstances are simply more dire than others.

Obama has consciously evoked Lincoln, but there may prove to be something of the Gerald Ford about his role. A step forward was made in vexed international relations during the Ford presidency when the Helsinki Accords were signed. No, this is not a development that should be credited to Ford, but it also was one that he allowed to go ahead, ignoring calls from his right that the Accords represented too-great concessions to the Soviets.

Even though Obama is stepping into office as Mr Fixer-Upper, he will not have to emulate Ford in pardoning his predecessor, unless someone finds a way of putting George W Bush in the dock. Like Ford, Obama has to overcome the unfortunate inheritance of a divisive presidency that has damaged American lives and damaged America abroad - and even then, not quite; Nixon's time in office saw significant progress in foreign relations, notably regarding China. Oddly enough, until this week when the official Chinese press turned on Bush and Obama to savage both of them, Beijing's line had been to praise Bush 43 for improving US-China relations.

Ford presided over a worsening US economy and unless Obama achieves massive success very quickly, so will he. The obvious difference being that Obama has been much faster out of the starting blocks, and much more inspirational in making his run.

Most of all, if the Obama presidency succeeds - in every of the myriad challenges, the wars, the economic crisis, the triumph of security over terrorism along with the restoration of constitutional rights - then the Obama years will fit the title of Ford's post-presidential biography, A Time to Heal.

Nelson Mandela's biography was entitled A Long Walk to Freedom. On CNN, John King reminisced that the Obama inauguration reminded him of the spirit of the 1994 inauguration of Mandela as South Africa's president. The comparison was given added gloss by Mandela's congratulatory letter to Obama.

Yes, there are similarities - the obvious one being that both are the first black people in their respective countries to have become head of state and government, the other the world view of both representing hope after deep trauma - but comparison of the two men not only does not bear deep scrutiny, but is a disservice both to Mandela and to Obama.

As someone who covered the Mandela presidency, I agree that there are deep similarities in the two inauguration days. But not in the challenges, nor in the approaches and styles of the men facing them. In many ways, Obama is seeking, as per his inauguration speech, to restore the American Dream; Mandela's presidency was about the first steps into a wholly new South Africa. The economic challenge for 1994 South Africa was to widen and deepen economic opportunities for all, including through a mechanism of affirmative action; Obama's project is about rebuilding a gravely wounded economy. A third significant difference; Obama is reshaping US relations with the world; Mandela's South Africa was welcomed by a world abounding with goodwill towards it. Obama is clearly bent on a detailed command of the policies and actions of his administration; Mandela delegated a lot of the nuts and bolts to his then deputy president Thabo Mbeki. The equivalent would be Obama leaving much of the running of the show to Joe Biden while Obama sets about being the chief priest of national reconciliation; not a likely scenario.

I am not a fan of Margaret Thatcher but there is something about her time in office - the firm hand on the tiller, the revolutionary approach to domestic economic and foreign policy - that may in time be a point of comparison by the end of the Obama presidency. Obama has signalled a clean break with the Bush past, even though he has retained some of Bush's office-bearers and incorporated Republicans and even erstwhile Democratic foes (notably Hillary Clinton) into his team. But like Thatcher, Obama is navigating a wholly new course and pushing firmly ahead on the throttle, and like Thatcher, is making firm choices against a background of a troubled economy. (While we're on autobiography titles, Thatcher's were The Path to Power; The Downing Street Years; and Statecraft: Strategies for a Changing World. Obama, if he does not want to recycle Ford's book title, could already use the first of Thatcher's, would have to omit the second, and success could earn him the right to copy the third.)

This blog joins the avalanche of others amid the first week of the Obama presidency. Await the tsunami after the first 100 days and the end of the traditional honeymoon period. Then the first provisional judgments may be made on the opening performance of the Obama presidency, and please, let us all do so on the merits rather than by spurious comparisons (or by political racial profiling that means that every inspirational black leader must needs be compared to Mandela). Am I, after these first few days, pro-Obama? Of course. We're so alike. We're both tall, thin, and 47 years old.