Quick-thinking car hire staff helped identify the Westminster attacker after recognising the licence plate of the vehicle he used to mow down and kill two people.
The Hyundai 4x4 was hired from a branch of Enterprise in Birmingham.
It was then driven to the centre of London where Masood used it to crash into tourists and other pedestrians crossing Westminster bridge just after lunchtime on Wednesday.
He then jumped from the car and raced around the corner to the entrance to the Palace of Westminster where he stabbed and killed an on-duty police officer before eventually being shot dead by armed police.
An Enterprise employee saw the number plate of the car in news reports of the deadly attack online.
They double-checked the plate on the company's computer system and then immediately telephoned police.
Enterprise said that it was co-operating fully with the authorities.
In a statement the car hire giant said: "We can confirm that the car used in the tragic attack in London yesterday afternoon was one of ours.
“An employee identified the vehicle after seeing the licence plate in an image online.
"We ran another check to verify, and immediately contacted the authorities.
“We are co-operating fully with the authorities and will provide any assistance that we can to the investigation.
“Our thoughts are very much with the victims of this terrible tragedy.”
In a statement, Birmingham Central Mosque chairman Muhammad Afzal said: "Nothing justifies taking lives of innocent people.
"Those responsible must be brought to justice to protect good, in our constant fight to eradicate evil within humanity."
He added: "The Islamic faith does not allow anyone to take the life of others.
"No religion justifies the indiscriminate killing of individuals in such a barbaric and heartless way, and such acts only serve to differentiate between the misguided and the just.
"We call upon those that may have even a shred of sympathy for the like-minded terrorists to shake their conscience and realise that such acts are the work of evil and not the work of God-fearing people."
A peace vigil will also be held in Birmingham.
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