Public security

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MI5 watching 3,000 ‘active’ subjects at all times – here’s how they track terror suspects on British streets

MI5 will usually reveal after an atrocity whether the attacker was known to their investigative teams or if they were not an active subject of interest.

The agency and police teams were tailing crazed Streatham jihadi Sudesh Amman when he launched a bloody knife rampage yesterday.

Amman, 20, was put under surveillance after being released from jail just days ago for a string of terror offences.

He was among around 3,000 active subjects of interest (SOIs) being tracked by the super-secret British agency at any one time.

But with so many potential terrorists roaming Britain's streets, MI5 need a full range of techniques to keep eyes on their suspects.

Here is a list of how spooks track terror suspects according to Sky News.