21/7: timetable of terror alert

Here is a timeline of today's events which saw terrified passengers evacuated from Tube trains and a bus after four more explosions across the capital.

* 12.25pm police evacuate Shepherd's Bush Tube station on the Hammersmith and City line following an attempt to set off an explosion.

* 12.30pm Emergency services are first called to Oval Tube station. Around 20 or 30 passengers are evacuated from a Tube train saying that they had seen "white smoke". There are also reports of a man dumping a rucksack in a carriage then fleeing as the doors closed.

* 12.45pm London Ambulance Service sends five vehicles to Warren Street Tube station after reports of a rucksack exploding on a train in a tunnel just outside the station.

* 1.15pm Pubs and offices near Warren Street Tube station are evacuated.

* 1.22pm London Underground says it has suspended services on the Hammersmith & City, Victoria and Northern lines.

* 1.30pm The driver of the number 26 bus reports hearing a bang followed by a smell of smoke coming from the upper deck while driving along Hackney Road, Shoreditch. Upstairs he finds the windows blown out.

* 1.45pm Transport for London confirms it has imposed a Code Amber at all three affected Tube lines which means trains are taken to the next station and passengers evacuated to above ground.

* 1.45pm Police with sniffer dogs comb the pavement along Euston Road, near Warren Street and the surrounding area.

* 2.05pm Transport for London confirms that four lines - the Hammersmith and City, Northern, Bakerloo and Victoria - remain suspended.

* 2.24pm Metropolitan Police confirm armed officers have been deployed to University College Hospital where they are dealing with an incident.

* 2.40pm An initial examination at Oval shows that there is no trace of chemical agents.

* 2.45pm Downing Street confirms the Government's civil contingencies committee - known as Cobra - would be meeting in response to the latest incidents.

* 3.10pm London Underground says the Piccadilly and Bakerloo lines have also been suspended, although no incidents have been reported on those lines.

* 3.20pm British Transport Police confirm no trace of chemical agents have been found at Warren Street station following the incident there.

* 3.25pm London Fire Brigade says officers are deployed at Warren Street London Underground station in full protective equipment as a precaution in order to examine the scene.

* 4pm Armed police and dog handlers arrive at Shepherd's Bush to begin searches of streets that had earlier been sealed off.