The chilling (and balaclava-clad) face of modern British policing: London siege reveals armed-to-the-teeth team preparing for the Olympic Games

Bristling with guns, his face masked, a police officer moves in on a suspected suicide bomber.

Just 91 days away from the start of the Olympics, the dramatic scene gave a foretaste of what can be expected this summer after a man threatened to blow himself up in a busy office block.

Thousands were evacuated, Tube stations were closed and streets locked down over a wide area of London's West End.

Snipers, bomb disposal squads, nuclear biological and chemical warfare specialists and dozens of armed police were scrambled to the building on Tottenham scrambled to an office block on Tottenham Court Road, one of the city's busiest shopping streets.

The face of modern policing: This picture shows the specialist combat gear worn by the armed police units responding to the siege in central London yesterday

As marksmen took up positions on rooftops, office workers were banished from their buildings while others were trapped as the man with canisters strapped to his body yelled that he would 'blow everybody up'.

For three hours, as negotiators spoke with the man, named last night as 49-year-old Michael Green from Hemel Hempstead, terrified office workers and children were held back behind police cordons.

Last night one of the workers inside the building, Abby Baafi, 27, told how a man had arrived at the headquarters of an HGV training company shouting threats.

'He said he doesn't care about his life, he doesn't care about anything he is going to blow up everybody,' she said. Amazingly, Miss Baafi said she recognised him as a former customer of the firm, AdvantageHGV, which arranges training for lorry drivers across the country.

'He was not quite stable – mentally stable. He turned up, strapped up with gasoline cylinders, and threatened to blow up the office. He was specifically looking for me,' she added.

The quick-thinking training director gave him the slip by denying she was the woman he was hunting and she was allowed to leave the building.

Armed to the teeth: As a cafe worker looks on in surprise, Met police snipers arrive with weapons stowed in holdalls to get into position on rooftops around Tottenham Court Road

Dixon of Dock Green... balaclava: A member of Scotland Yard's firearms unit gives the thumbs up after arriving on the scene of yesterday's hostage crisis Taking aim: A police marksman has the hostage taker in his sights

She said the man had wanted his money back after repeatedly failing one of the company's HGV courses. Miss Baafi was speaking while police negotiators painstakingly persuaded him to give himself up without detonating his canisters. The hostages were seen hurling computer printers, filing cabinets and televisions out of office windows before the man finally let them go. Members of the Metropolitan Police's CO19 firearms unit – several of them former soldiers – covered the windows and entrances with their weapons while others covertly entered the block. As marksmen covered his every move, the man stripped to the waist, hands in the air emerged tentatively on to the pavement where two uniformed policemen walked forward and searched him. Special forces soldiers based in London including the SAS had been put on alert while members of the RAF's nuclear, biological and chemical warfare group was dispatched to the scene. 'You need the specialist chemical people on the ground to make sure you can identify what is there in case it is seriously dangerous. In the case of the canisters it was unclear at the outset,' a senior security official said last night. 'Remember the Tokyo subway incident, there's always a fear in the back of the mind you are dealing with something potentially catastrophic.' Sarah O'Meara, who also works for website the Huffington Post, said they evacuated their offices in nearby Capper Street after being alerted by a woman who ran into the building. Medical courier Gentian Mancjan was parking his van opposite the building when he heard the suspect shouting.

Combat team: Tooled up and ready to raid the building, armed officers are seen on Tottenham Court Road. Special forces and police firearms units have trained together in urban warfare tactics

Apprehended: Regular officers lead away the suspect, unharmed but cuffed and stripped to the waist, after the massive police operation this afternoon

He said: 'He shouted “I'll blow myself up! I'll blow myself up!” and then ran in the door. I thought it was a joke at first because no one was panicking but then I saw people coming out. I saw a woman shaking and saying “My friends are in there”.'

Ahmad Salim, 31, an account director for advertising agency TBWA, saw captives being forced to throw office equipment onto the street. 'They were throwing out printers, monitors, filing cabinets, it was smash, smash, smash,' he said.

He said he saw the man on his mobile phone locked in negotiations with police. 'He was pacing up and down, on the phone. He was drinking out of a cycling water bottle.

'It was dark liquid, something other than water, it could have been juice or alcohol.'

Actress Frances Barber, 53, was among those who were affected by the incident, ordered to stay within a building as events unfolded. Barber, who appeared in the last series of Doctor Who, kept her followers updated on Twitter. '**** a duck am in middle of hostage sitch in Tott Ct Road. Can't get out. We are all hostage inside,' she wrote.

'Police won't let us out. Tott Ct Rd deserted. All shops, cafes, etc evacuated. Police everywhere. We are not allowed out.' Last night police confirmed Green did not have explosives on him.

Police commander Mak Chishty said: 'Specialist negotiators were called to the scene along with colleagues from the London Ambulance Service, the London Fire Brigade and the Specialst Firearms Unit.

'During the course of the incident a number of people inside the building left peacefully.