The Met had long experience gained from the years of dealing with the IRA, he said, and "we've now upped our game". London's police forces today work more closely with the intelligence services than any other police in the Western world. The capital could feel safe during the 2012 Olympics, he assured radio listeners. Less than two hours later the bombs went off.
The immediate response by the emergency services has been universally praised. But Sir Ian knows that he now faces running an extraordinarily complex criminal investigation. More than that, he also has to try to restore public confidence in a police and security service which detected no hint that the bombers were at work.
He knows also that he must do this from a difficult background - for, despite the Government's confidence in him, he knows that this confidence is not universally shared.
Sir Ian became Met Commissioner in February pledging to modernise one of the world's biggest police forces - of some 35,000 officers and 15,000 civilian staff - and make it truly representative of London's population by recruiting more women, gays, Asians and blacks. This has led critics, most particularly in the right-wing press, to sneer that he is obsessed with political correctness rather than with catching criminals in an area which has one of the lowest crime clear-up rates in the country - only one in five crimes reported to the Met ends in conviction. Nor have they been terribly keen on his insistence that the relaxation of cannabis laws should not be reversed and that indeed fixed penalty notices should be introduced for people possessing small amounts of the drug. And his position was not helped when an employment tribunal found that Sir Ian had racially discriminated against three white officers who were disciplined over alleged racist remarks made at a training day.
Blair's defenders, who call him a "thinking man's copper" who has for years been critical of the police service's "canteen culture", say the hostility to him is racist, and that the new Commissioner is fighting "a war for the soul of British policing". Sir Ian himself is sanguine. "You don't come into here without a pair of copper-bottomed trousers," he shrugs. "This is a very tough place."
The idea that he is a bit of a softie is belied, however, by some of his other ideas. He is in favour of biometric identity cards, wants a 9pm curfew on unaccompanied children under 16 in the West End, and thinks that bars and nightclubs should foot the bill for late-night policing in alcohol-fuelled city centres.
What links all these is not some political worldview, but rather an operational one. Ian Blair is interested in what works as well as what is fair.
He wasn't keen on ID cards until he began to understand the highly sophisticated technologies used by criminals in identity theft. His cannabis fixed penalty notices stem from frustration at the hours his officers spend dealing with offenders the courts don't then do anything about. Race and faith diversity are essential because it is impossible to police London effectively "without understanding the diverse communities we serve". Nor is there any point, he says, in "ducking the fact that most muggers are black", nor that the much criticised trebling of stop-and-search techniques among the capital's Muslims has produced dividends, even if these are too sensitive to be made public.
For all that, Blair's reputation as a reformer and a moderniser - and therefore "New Labour's favourite" policeman - is well-deserved. After university in Oxford (where he hoped to become a professional actor, until he took part in a drama competition with the comedian Mel Smith and decided he was out of his league), he joined the Met as a constable in Soho.
He rose rapidly through the ranks. In 1988, after a BBC documentary depicted detectives interrogating a rape victim, accusing her of lying, the young policeman wrote a book, Investigating Rape: A New Police Approach, which transformed procedures throughout the country. Its general approach is still in use. Not long afterwards, he was promoted to chief superintendent, working for Her Majesty's Chief Inspector of Constabulary at the Home Office.
Two years later he was back at the Met, when another television documentary prompted another initiative. Panorama showed detectives taking bribes from criminals, and a major investigation, Operation Gallery, was put in train, with Blair at the head.
His next move was to Thames Valley Police as an assistant chief constable, where he took charge of policing the Newbury bypass protest, in which he adopted the principle that the police had a duty to ensure that the rights of protesters and roadbuilders were both respected.
In 1998 he was appointed Chief Constable of Surrey, but held the post for just two years before returning to the Met as Deputy Commissioner to Sir John Stevens after being unsuccessful in his application for the £225,000-a-year top job .
In his five years as deputy to Stevens, he put in place a strategy of "multi-tiered policing", which included the creation of community support officers who patrol the streets without the full powers and training of a police constable. Traditionalists, including some very senior policemen, were highly sceptical, and opposed the idea fiercely. But there is now such widespread acceptance within police circles that the innovation has been an unqualified success that the Met's 2,000 community support officers are now being widely copied by other forces.
One of the qualities which has distinguished Blair from many of his colleagues, including fellow graduates, is that he avoids the social ghetto within which many officers confine themselves. Part of the police culture is that it is intensely self-reinforcing; friends and social contacts are often with other police officers, which can isolate them from the social, cultural and intellectual attitudes of the rest of society.
Ian Blair has avoided this. He has maintained his links with the academic world. He is a visiting fellow of Nuffield College, Oxford, and an honorary member of the senior common room of Christ Church. In 1998, he was made a visiting fellow of the International Centre for Advanced Studies, New York University, which is where he developed ideas about multi-tiered policing and community support officers. Socially he is as likely to be found at dinner with Mark Thompson, director general of the BBC, or with the novelist Ian McEwan as with fellow senior police officers or politicians.
All of which goes down well with outsiders, but less so in more traditionalist police circles. When he succeeded Sir John Stevens five months ago, Ian Blair pledged to modernise the force as well as to be more responsive to the public. Some say that is to do with the contrasting personalities of the clubbable Stevens and the more introspective Blair. "He tends to be reserved and self-contained," says one who knows him well. "It's true that those who don't know him can be highly critical. But those that know him well have a high regard."
Yet it is Ian Blair's agenda which also raises suspicions within the Met. His modernisation plan includes a wide-ranging shake-up of Scotland Yard to improve efficiency and save more than £300m from the Met's annual budget of about £2.5bn.
Until now among the sections to be scrutinised were the special branch and counter-terrorism units. The anti-terrorist unit has taken on more than 700 extra officers in the past two years, and it is notoriously hard to measure their efficiency. Blair's predecessor claimed that the anti-terrorist team thwarted eight potential atrocities. But value for money is hard to quantify, at no time more so than when a terrorist outrage like this week's has not been prevented.
Ian Blair has other ideas. He came up with the idea, which was backed by the Association of Chief Police Officers (Acpo), of a 5,000-strong "border guard force" made up of customs and excise officers, immigration staff and police officers, to combat organised crime and terrorism.
He has also proposed that we need laws to counter "acts preparatory to terrorism", most particularly because al-Qa'ida operates using very loose-knit cells.
Before Thursday's bombs, the Metropolitan Police had announced details of a massive security deployment plan, set to cost £224m, if London won its bid for the 2012 Olympics. After the events of this week, the fear may be that even that sum will not be enough.
Yet even so, there are many who feel that if decisions on matters as delicate as this, in times as charged as these, have to be taken then Ian Blair is as good a man to have in the hot seat as any. "He's always had an extraordinary ability to spot the potential for change, often long before anyone else," one of those who knows him well has been quoted as saying.
"Behind the scenes," said Tom Williamson, a former Met murder squad leader and later Nottinghamshire deputy chief constable, now a visiting professor at Portsmouth University, "he's been delivering wake-up calls to the service for the past 20 years."
It may well be time now for a more public one.
A Life in Brief
BORN 1953 in Chester.
FAMILY Married to Felicity; two teenage children.
EDUCATION Wrekin College, Shropshire, Harvard High School, LA and Oxford University.
CAREER Joined the Met in 1974. Helped to change rape investigations in the 1980s. Chief superintendent in 1991. Assistant chief constable of Thames Valley Police in 1994, then Deputy Chief Constable. Chief Constable of Surrey in 1998. In 2000, made Deputy Commissioner of the Met and Commissioner in 2005. Knighted in 2003.
HE SAYS "We must remain vigilant. It [terrorism] is a national issue, not just for London."
THEY SAY "Sir Ian's obsession with attacking 'Islamophobia' is now raising serious concerns." Melanie Phillips, columnist.