The day we were dreading
For some years London has lived under the shadow of the terror threat. Thursday's blasts were the grisly realisation of what many had quietly feared, but hoped would never happen.
According to those who were best informed, it was always a question of when, not if.
The former commissioner of the Metropolitan Police, Sir John Stevens said as much last year, in the wake of the bomb attacks on Madrid which left almost 200 people dead.
"[T]here is an inevitability that some sort of attack will get through," said Sir John in March 2004.
But who could have guessed that a damp and unseasonably chilly Thursday in July, would have been the "when" we had, to a greater or lesser degree, been dreading.
As Tony Blair subsequently noted, the start of the G8 conference in Gleneagles appeared to be the motivation for the series of deadly bomb blasts across London.
But there have been plenty of potential flashpoints before. The general election in May, major sporting events, Christmas shopping, the start of the wars in Afghanistan and Iraq - each has prompted a surge of anxiety, only to pass off without incident.
Tube commuters have long feared they would be a 'soft' target
Terrorism has long been a reality in Britain. But the devastating attacks on New York and Washington on 11 September 2001 took the threat to a disturbing new level - one where anybody at anytime could, conceivably, be a target, without any hint of a warning.
In the immediate aftermath of the 9/11 hijackings, Londoners started to contemplate the risk of copycat attacks on their city.
Office works and residents in tall buildings feared they could be caught up in suicide plane attacks, similar to those which brought down the Twin Towers in New York. Architects began to question the case for skyscrapers.
By the end of September, the government was warning of fresh al-Qaeda strikes, which could affect the UK.
"We are in a very dangerous situation," warned one Cabinet minister.
The following month saw anthrax attacks in the US, and once again the anxiety generated spread across the Atlantic. Company mail rooms began emergency procedures to deal with suspect packages. Government buildings were evacuated and a House of Commons sitting was even suspended as the climate of suspicion grew.
Chemical threat
The Doomsday warnings began in earnest a year later, when the Home Office issued a document detailing all the likely generic targets for a possible al-Qaeda attack on Britain, including train stations and airports.
The threat remains as high from here on in as it had to hitherto fore
Glenmore Trenear-Harvey
By early 2003, troops had been drafted in to Heathrow airport following intelligence which suggested there was a terrorist plan to shoot down an aircraft.
Then came talk, from MI5 supremo Eliza Manningham-Buller, of a possible chemical, biological or nuclear attack. It was a "realistic possibility" in a major Western city.
With each new warning anxiety levels were ratcheted up and then, for some at least, the fear melted away as life went on as normal and the spectre of terrorism took a backseat.
Yet the underlying mood of concern continued to grow, stoked by a series of events, from the ring of concrete barriers erected around Parliament to high profile arrests of terrorist suspects; from rehearsals of how the emergency services would respond to a strike, to discoveries of potentially lethal terror weapons.
Even the most maverick of stunts, such as when Fathers for Justice campaigners stormed the grounds of Buckingham Palace in fancy dress, were cast in the light of, "what if they had been terrorists?"
Reassurance and fear
Abroad, UK interests were established as targets. The bombing of the British consulate in Istanbul, which killed 14 people, unsettled the resolve. In the Yemen, the embassy was closed indefinitely because of security fears.
On edge: A security alert forced this plane to land in London last year
Somewhere along the line - the covert nature of intelligence means it's not entirely clear when - the official threat level was raised by MI5, Britain's domestic intelligence agency, from "substantial" to "severe general".
Reports of how intelligence experts had helped foil planned attacks drew a mixed response - a sense of reassurance that the authorities might have the upper-hand, but inevitably also a feeling of vulnerability; a belief that the "when" spoken of by Sir John Stevens was looming ever closer.
The attacks on Madrid's train network in March last year, in which 191 people died, sent alarm levels soaring once more, particularly among commuters who were reminded of the vulnerability of any public transport network.
Some commentators suggested Londoners were being ruled by an irrational fear, particularly over the impact of a chemical or biological strike.
"Do we really know they have these dreadful weapons?" Bill Durodie, of King's College's Centre for Defence Studies, asked through the BBC News website in June 2003. "Since September 11th the actuality of terrorism remains rather more mundane."
Paradoxically though, the weeks before Thursday's simultaneous rush-hour strikes on London had been characterised by an ever so slightly more relaxed mood. In June, in an advisory note to leading business, MI5 said the terrorist threat had been downgraded back from "severe general".
By Thursday morning itself, the story uppermost in Londoners' minds was the buoyant news of how, the day before, the capital had won its bid to stage the Olympics in 2012.
The mood of optimism barely had time to take root before it was shattered by news of the blasts. The wave of attacks that had been unfolding around the world since 11 September had, it seemed, finally caught up with London.
And for those seeking reassurances from the aftermath of turmoil, believing that it could have at least been worst, intelligence analyst Glenmore Trenear-Harvey sounds a cautious note.
"The threat remains as high from here on in as it had to hitherto fore."
I'm sure he's fine, maybe he's just adjusted his priorities given today's events.