Updated March 23, 2017 19:17:52

Photo: People rushed to help those injured in the attack on Westminster Bridge in London. (Reuters: Toby Melville)

A suspected Islamist terrorist began his deadly attack in London on Wednesday by driving at high speed into pedestrians walking along the footpath on Westminster Bridge.

Two of the four confirmed deaths were pedestrians hit by the car — and they would have had little room to escape the attack.

Four lanes of traffic and two footpaths are squeezed on to the 26 metre wide, 250m long bridge.

There are no fences or bollards that separate pedestrians from the busy traffic.

The busy crossing over the Thames is one of the most popular spots visited by tourists looking to get a picture of Big Ben and is often visited by school children.

Here is what else happened on the iconic bridge before the attack moved to the grounds of the Houses of Parliament.

A woman had to be pulled from the Thames

She had serious injuries, according to the Port of London Authority.

It is not known if she jumped into the river to avoid the attack or was knocked in after being struck by the speeding car.

Tourist Steve Voake was walking along Westminster Bridge when the attack happened.

"There were a couple of bodies on the other side of the bridge and then the side I was on there was a body in the water with blood around it," he said.

Police were among the injured pedestrians

Britain's most senior counter-terrorism officer Mark Rowley said three police officers were injured on the bridge.

Two of them are still in a serious condition.

He said the officers were returning from a commendation ceremony.

A photographer heard a body land near him

Reuters photographer Toby Melville was below Westminster Bridge taking pictures for an unrelated story when the attack happened.

He said he turned around after hearing a thud to see a man lying "about 10 yards" away.

"There was a lot of blood coming from his head. I thought this must be a domestic or horrible accident," he said.

Three French school students were injured

The high school students were injured as the attacker's car tore across the bridge.

A French government plane will fly the families of the three teenagers to London, according to French President Francois Hollande.

London is a common destination for French school trips.

Mr Hollande expressed France's solidarity with Britain "in this tragic ordeal".

"The British and French services are in close contact to conduct the investigation," he said.

ABC/wires

Topics: terrorism, united-kingdom, england

First posted March 23, 2017 11:44:44