Following the London Bridge terror attack, which took the lives of 7 people, the capital's streets became host to the first deployment of "Blue Thunder".

The elite SAS unit was deployed after a vehicle ploughed into pedestrians on London Bridge before its knife-wielding occupants continued the attack on foot on Saturday night (June 3).

The Birmingham Mail has put together a guide to explain who Blue Thunder are, how the unit got its name and more.

Who are Blue Thunder?

Blue Thunder act on orders from the Home Secretary and can be scrambled within a moment's notice.

The squad have been dubbed 'Blue Thunder', because they travel around in an unmarked dark blue Eurocopter Dauphin helicopter.

The civilian-style helicopter is used to transport Special Forces troops around the country quickly and under the cover of secrecy.

The highly-trained unit flew in from one of three airfields and two airports where they are stationed around the country.

A chopper was photographed landing at London Bridge after three terrorists ploughed into pedestrians before embarking on a knifing rampage in bars and restaurants.

It is said the team were looking for the missing suspected terrorist.

What is their background?

They are a 70-man strong unit formed after the 2015 Paris attacks and trained in tackling domestic terror scenarios.

The unit has been rehearsing terror scenarios for more than a year after they were designated the country's first line of defence against any attack on UK soil.

The troops work directly under the command of counter-terror police. According to reports, the team serve alongside police liaison officers, of which there are thought to be seven.

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What is happening now?

12 arrests in connection with the attacks came as Prime Minister Theresa May warned that Britain is in the grip of a spate of copycat terror plots. It also emerged that an off-duty Metropolitan Police officer was among the 48 people injured by the terrorists. Meanwhile raids have been carried out in Barking and Newham.

London terror attack: Neighbours hear gunfire and 'loud explosion' as police continue raids at Barking and Newham

May warned terrorism had a "new trend" and unveiled a blue print for a tough crackdown in the wake of the massacre.

She declared "enough is enough" in the rousing speech - her second response to a terror attack outside Downing Street in less than two weeks.

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