MI5 knew Westminster Bridge attacker Khalid Masood in 2004

Khalid Masood, 53, was investigated as a potential extremist in 2010, but the first trace of him in the security service’s records dates back to April 2004.

The inquest into the deaths of Masood’s victims has heard his phone number appeared in the contact list of someone known to Operation Crevice, which smashed a plot to blow up the Ministry of Sound nightclub, in April 2004.

At the time, Masood was living in Crawley, West Sussex, which was the epicentre of the investigation that prevented what was then the biggest terrorist plot in Britain.

He appeared on MI5’s radar again six years later as a potential facilitator for extremists travelling to Pakistan through
Saudi Arabia, an MI5 witness has told the hearing.

As a result, Masood was designated as an MI5 “subject of interest” (SOI) – meaning someone it is trying to investigate.

By the end of the year, investigators decided he wasn’t a threat and he was removed from the live SOIs list.

Over the next four years he intermittently popped up as a contact of people involved in the banned network once headed by the hate preacher Anjem Choudary.

Masood drove a 4×4 into pedestrians on Westminster Bridge, killing Kurt Cochran, 54, Leslie Rhodes, 75, Aysha Frade, 44, and Andreea Cristea, 31, before fatally stabbing PC Keith Palmer at the gates to the Palace of Westminster.

The IS sympathiser was shot dead by armed officers after an attack that lasted less than two minutes on 22 March last year.

Masood, who endured a troubled upbringing, converted to Islam in 2003 after spending time in prison for a knife attack outside a pub.

At the time, his attack was the worst terrorist atrocity in Britain since 2005.

The inquest continues.