London. After the bombs

THE capital's Underground rail system has never been a comfortable place to travel. Crowded, unreliable and smelly, it is endured by Londoners rather than loved. Since three simultaneous bombs went off on three Underground trains at 8:50am last Thursday, followed just under an hour later by a bomb on a bus, the discomfort has taken on a macabre quality. Backpacks attract nervous looks. People try too hard not to catch the eyes of young men with brown skin. Much has been made of Londoners' Blitz spirit in the past week. But the comparison jars: people went down into the Tube to shelter during second-world-war air raids. Now the up escalator feels like the route to safety.

In one sense, London is almost back to its teeming normal. Passenger numbers on the Tube are only slightly down when the reduced service is taken into account. Companies had emergency plans to cope with disruptions to their businesses, an innovation since the attacks of September 11th 2001, but decided not to put them into operation. The stockmarket took just a day to recover, indicating that investors were hardly surprised that London had become the target of a successful terrorist attack - and that they thought it had come through the ordeal.

But this normality is more fragile than it looks. Identifying victims torn apart by the bombs is difficult and the process for officially confirming deaths slow. Every day has brought new newspaper photographs of the smiling faces of dead people. Pictures of the missing are still pinned to the fence outside King's Cross railway station. Grieving will not become private until they are taken down.

Britain's security services remain on their highest state of alert. The police have been worrying that the terrorists would carry out another attack, as the bombers who killed commuters on trains in Madrid in March last year were apparently planning to do. On Saturday night around 20,000 people were evacuated from the centre of Birmingham, after a suspect package was found on a bus. This turned out to be a false alarm. But a second successful attack would strike a nation that is in an anxious state of mind.

Hence one reaction to the news on Tuesday that police had identified four British men who had carried the bombs and blown themselves up: if they are dead, then they cannot kill again. But it also raised a disturbing thought: that Britain now has homegrown suicide-bombers who think the Dar al-Harb, the Abode of War, can be reached by boarding a Thameslink commuter train.

The terrorists gave no warning and the security services had not picked up any hint that an attack might take place (in fact the threat level had recently been downgraded from “severe general” to “substantial”). So the police started with no leads.

From the narrow perspective of the investigation, it was fortunate that the fourth bomb exploded on a bus rather than the Tube. Forensics experts could study the damage from a blast that had not been magnified by being confined to a tunnel.

This told them two things. First, that the bomb was no bigger than 10lb (4.5kg). That makes sense: the power of a charge grows with the volume of explosive, so to get a much larger explosion, say twice the size, the weight of explosive would have to be cubed. A really powerful device would be too heavy to carry without looking conspicuous. Second, the explosive was not a homemade cocktail of ammonium nitrate and fuel oil, but a high-grade explosive of the type used by the army or in industry. That, plus the synchronised timing, pointed towards a well-trained terror cell and inspired comparisons with the Madrid attacks, when a foreign al-Qaeda cell left timed devices on four trains carrying commuters.

But that working assumption changed on examination of CCTV film from cameras at King's Cross. This showed four young men with backpacks standing together on the station concourse before going their separate ways. It was nearly 8:30am, about 20 minutes before the Tube attacks. The bombers appeared to want recognition. At the epicentre of the blasts, police found personal documents, including credit cards and driving licences, that identified three young British Muslims from Pakistani families. One, a teenager called Hasib Mir Hussain, had been reported missing by his parents in Leeds on the day of the attacks. The fourth man, identified after a raid on a house in Aylesbury in the south of Britain, was a Jamaican-born Briton in his thirties - a strikingly different profile.

At 6:30 on Tuesday morning, police raided six addresses connected to the men in and around Leeds. They found more explosives, evacuated about 500 people from the surrounding area and made one arrest. Explosives were also found in a car that had been left in the station car park in Luton. Police now think that three men travelled down from Leeds and were joined at Luton by a fourth. The men - Mr Hussain; Shehzad Tanweer aged 22; Mohammed Sadique Khan aged 30; and a fourth as yet unnamed - then took the train from Luton to London.

A return to politics

The Madrid bombs caused political damage. The attacks took place just before an election in which the opposition argued that the Iraq war had imperilled its citizens. The government's readiness to accuse Basque terrorists contributed to a crushing electoral defeat.

Britain will be different. The main opposition party supported the Iraq war and has praised Tony Blair's statesmanship. Charles Kennedy, leader of the Liberal Democrats, the one big party against the war, has raised questions about Iraq, but has been careful not to say the bombs prove his party was right. A few marginal voices have argued that the attack was payback for Iraq, but this is unlikely to wash. An ICM poll for the BBC's Newsnight showed no increase in support for withdrawing British troops.

What will change is the politics of security. Civil liberties are a minority interest in Britain: a poll conducted over the weekend by Populus for the Times showed that 86% of those surveyed supported giving the police new powers to arrest people they suspect of planning terrorist attacks.

But the minority includes many judges, journalists and MPs and, back in March, the government had to fight to get Parliament to approve legislation to bring in control orders - a set of extra-judicial measures to deprive suspects of some of their liberties. Further restrictions on civil liberties may now prove easier to secure when MPs return to Parliament in the autumn. Tony Blair is already talking about new laws aimed at those involved in the preparation of and incitement to terrorism. If this happens, it would be the fourth attempt to toughen anti-terror laws since 2000.

More legislation may make Britons feel safer, but it will not tell them what they most want to know: who supplied the bombers with equipment and trained them to use it? And how many more British citizens are queuing up to martyr themselves beneath the streets of London?