A young cyclist accused of killing a mother-of-two by ploughing into her on a racing bike sprang up and began shouting at her as she lay mortally injured in the street, a court heard.

Charlie Alliston was allegedly riding a fixed wheel track bike with no front brakes when he crashed into 44-year-old Kim Briggs as she crossed Old Street in east London in February last year.

Alliston, then aged 18, is on trial at the Old Bailey charged with manslaughter and causing grievous harm by wanton and furious driving under the 1861 Offences Against the Person Act.

Prosecutor Duncan Penny QC read out a statement from eyewitness David Callan.

Mr Callan described how he was walking along Old Street at about 12.15pm.

He said: "I had my head down looking at something on my mobile phone when I heard a shout.

"It was a loud shout and seemed like a male voice conveying urgency like a warning or alert.

"It made me look up immediately, just in time to see a collision between a cyclist and a pedestrian."

He said HR consultant Mrs Briggs was not using the crossing some 30 feet away.

He went on: "The cyclist flew through the air and the pedestrian fell at the point of impact.

"The cyclist clattered to the ground further down the road but quickly sprang to their feet and shouted something at the pedestrian as they took a step towards the pedestrian who lay on the ground.

"It seemed like the same voice I heard immediately before the collision."

Mr Callan said he saw other people had come to her aid so continued on his way.

Jurors heard Mrs Briggs suffered "non-survivable brain injuries" and died in hospital a week later.

The court has heard Alliston's "fixie" bike had no front brake so was not legal to use on the road.

In January last year, he had bought the £700 Planet X bike second-hand for £470 telling the vendor William Ringwood he used to be a courier and wanted to use it for track cycling.

Jurors have been told that crash investigators had concluded Alliston would have been able to stop and avoid collision if the bike had been fitted with a front brake.

Alliston, now 20, of Trothy Road, Bermondsey, south London, denies the charges against him.

Crash investigator Edward Small studied CCTV of the collision which was shown frame-by-frame in court.

He told jurors Alliston was seen in the footage beginning to swerve to take evasive action as he approached the pedestrian.

He was a minimum of between 6.65 and 9.65 metres away from Mrs Briggs and travelling at an average speed of 18mph, jurors were told.

Mrs Briggs stepped into the road 3.8 seconds before the crash, Mr Small said.

The investigator also carried out tests comparing the stopping distances of a police issue mountain bike, Alliston's Planet X bike and a fixed whee

The court heard that Alliston was doing between 10mph and 14mph as he tried to avoid the collision.

Mr Small concluded that if Alliston had front brakes on his bike, he would have been able to stop before the point of impact.

Jurors were also told that, after the crash, the defendant changed the wheels on his bike but the original set was later retrieved by police.