An ISIS linked plot to attack Britain allegedly led by a suspect known as 'The Surgeon' has been smashed by police and MI5.

4 men in their early 20s were arrested in West London yesterday, with one suspect Tasered by firearms police.

Officials swooped amid heightened fears that fanatics who have returned from Syria are planning a high-profile gun attack or a beheading.

It is understood to be the first plot in Britain that is directly linked to the IS terrorists responsible for the murders of British hostages Alan Henning and David Haines.

The 21-year-old nicknamed 'The Surgeon' was arrested by armed police who rushed his family home on an estate in North Kensington, where he lives with his mother and sister.

Witnesses said a team of armed officers dressed in all black stormed the house at 4.30am yesterday after throwing in stun grenades.

Senior sources said one of the four men was a suspected Terrorists, who had recently returned to the UK from Syria.

The Metropolitan Police said the men were arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.

Sources said the planning was at an early stage but public safety had been paramount in the decision to act.

One line of inquiry is that the men may have been planning a copycat attack in the wake of sickening propaganda videos of "Jihadi John" beheading Mr Henning and Mr Haines in Syria.

The possibility of a firearms attack is also being investigated as officers search cars and addresses across central and West London.

Last month, raids were conducted throughout Australia amid intelligence that IS were planning ‘demonstration killings’ there, reportedly including a public beheading.

Britain already has terrible experience of such an attack, although the two Terrorists maniacs who beheaded Lee Rigby outside Woolwich barracks last year were not linked to Syria.

The raids in Ladbroke Grove come at a time when police activity is at its highest level since the July 7 bombings in 2005.

Officials are particularly worried by the prospect of a so-called ‘lone wolf attack’, which requires little planning and could be carried out with a knife or firearm.

Police have stepped up armed patrols and searches, while specialist officers have been visiting extremist sympathizers and those who have been to Syria.

An ISIS video released online last week urged fanatics in the UK to strike.

It showed a British “jihadist”, believed to be Omar Hussein, a former security guard at a Morrisons supermarket, calling on ‘all the brothers in the UK’ to rise up.

The militant urged fellow fighters to travel to Syria and Iraq to join the extremist group in its self-proclaimed caliphate.For those who cannot make the journey, Hussein said: ‘You can cause terror right from within.’

Security services and politicians have long warned of the prospect of an IS plot here.

In August, the threat was raised from substantial to severe – meaning that an attack is highly likely.

This is thought to be the seventh plot in Europe involving Terrorists who have returned from Syria, but only the second in Britain, and the first that has been directly linked to Islamic State.

One case, which is due to be heard this month and is subject to reporting restrictions, involves two men who have been charged with planning terrorist offences in this country.

Other plots have been uncovered in France, Italy and the Netherlands.

In May, Mehdi Nemmouche, 29, who had fought with IS in Syria, was arrested after three people were shot dead in a Jewish museum in Brussels. Police said he had in his possession a Kalashnikov rifle, a handgun and a sheet emblazoned with IS logos.