London attacker acted alone and motive may never be known, say investigators

British anti-terrorism police investigating deadly attack outside parliament have concluded that Khalid Masood, the man behind the attack, acted entirely alone for reasons that may never be known.

British-born Islamic convert Masood, 52, was shot dead on Wednesday after killing four people including a policeman in a rampage on Wednesday when he rammed his car into pedestrians and tried to force his way into the parliament building in central London.

Islamic State claimed responsibility for the attack and police inquiries since have concentrated on whether Masood was acting with accomplices.

In the most detailed breakdown yet of events on Westminster Bridge and parliament on Wednesday, police said that the entire attack lasted a mere 82 seconds. After four days of intensive inquiries across England and Wales, involving hundreds of officers, the Metropolitan police said they had so far failed to establish the reason for the attack. It is continuing to look at whether Masood was prompted by online propaganda by Islamic State, which has claimed he was a “soldier”, or whether he had some other sense of grievance.

Deputy Assistant Commissioner Neil Basu said there was no intelligence to suggest further attacks were planned.

“We still believe that Masood acted alone on the day, and there is no information or intelligence to suggest there are further attacks planned,” he said in a statement.

Although 11 people were arrested in the aftermath of the attack, nine have since been released, with no further action to be taken. A 58-year-old man arrested in Birmingham remained in custody on Saturday while a 32-year-old woman from Manchester has been released on bail.

Police are investigating media reports that Masood checked his encrypted messaging service WhatsApp – or even sent a message – just before the attack, which hinted at others being involved. The police statement confirming that he was a lone actor does not appear to support suggestions that he had been in touch with an accomplice.

Basu, who is the senior national coordinator for UK counter-terrorism policing, said that even if he acted alone, police need to give as much of an explanation as possible to reassure Londoners, and to provide answers and closure for the families of those killed and the victims and survivors of this atrocity

“We must all accept there is a possibility we will never understand why he did this. That understanding may have died with him,” he added.

“Nevertheless we are determined to understand if Masood was a lone actor inspired by terrorist propaganda or if others have encouraged, supported or directed him.”

The police, having reconstructed the attack, said it had begun at 14:40:08 when Masood’s hire car mounted the pavement on Westminster Bridge, weaving along the footpath and road until 14:40:38 when he crashed into the perimeter fence of the Palace of Westminster.

He left the car at 14:40:51 and was shot by a police firearms officer, part of the close protection team of the defence secretary Sir Michael Fallon, in the palace courtyard at 14:41:30.

At 14:40:59, the first 999 call was made to the Met reporting the incident.

Basu said the investigation was continuing and appealed for anyone who had spoken to Masood in recent months, especially in the days leading up to the attack, to contact the police. They are still trying to establish whether he had been “inspired by terrorist propaganda or if others have encouraged, supported or directed him. If the latter proves to be the case, they will face justice.”

Before he launched Britain's deadliest attack since the 2005 London bombings, Masood was considered by intelligence officers to be a known criminal who posed little serious threat.

He had shown up on the periphery of previous terrorism investigations that brought him to the attention of Britain's MI5 spy agency.

He first came to the attention of the authorities in November 1983 when he was found guilty of causing criminal damage. His last conviction came 14 years ago in December 2003 for possession of a knife.