A drug addict from a wealthy family treated a child actor and his aunt as "worthless" when he mowed them down in a stolen car to evade police, a court heard.

Convicted car thief Joshua Dobby, 23, was out on licence when he ploughed into Makayah McDermott, 10, and Rosie Cooper, 34, as they walked along Lennard Road in Penge, south London.

Dobby, who had 53 previous convictions dating back to the age of 13, admitted their manslaughter and injuring another little girl in August last year.

As he appeared at the Old Bailey for sentence, Makayah's grandfather Martin Cooper told how he watched helplessly as Dobby lost control and launched the car at his family.

In a statement, he said: "On that day, I was there. I watched the car drive into and over all five members of my family.

"I watched as the driver of the car made no attempt to stop or apply the brakes and no attempt to swerve.

"In front of my eyes, my daughter Rozanne and my grandchildren all became worthless in the eyes of the man driving the car, a means to an end.

Makayah McDermott was just 10 years old (Oli Regan/BAM/PA Wire)

"They all became expendable and their only value was to create a scene of death and destruction, forcing the police to end their pursuit of him.

"How long did this man evade the police? An hour, a day, a week? This man's life gravitated to the police.

"For the sake of a day or two on the run, he sacrificed the life of my daughter and grandson, killing them and mutilating my granddaughter."

Dobby wept in the dock as prosecutor Anthony Orchard QC outlined the facts of the case.

On the afternoon of August 31 last year, the Cooper family were on their way to have ice creams and play on the swings.

Dobby was driving a black Ford Focus at three times the speed limit down one-way roads and jumped red lights before he lost control, hit a bollard and launching the car into the group.

He leapt out of the wreckage and fled on foot, leaving police officers to try desperately to save the victims.

​Makayah died from 40 injuries and his aunt had 53 wounds while another young child suffered serious leg injuries.

Dobby was heard to shout: "I've killed her! I've killed her!" as he was pursued by police on foot.

After he was arrested, he said: "I was driving I admit it. I should have just stopped.

"I don't want to go back to jail, now I might have killed innocent people."

The court was played dramatic police dash cam footage of Dobby's erratic high-speed driving before the accident.

In a letter from jail, he told his girlfriend: "After all this shit, I swear by almighty God that I will never put another drug in my body. I take oath on that.

"Two people have lost their lives cos of my selfish f***ing actions and it all boils down to drugs.

"It should have been me that lost my life but it wasn't. I still have a life and I'm determined to do something with it for the sake of that child."

Giving evidence, Dobby admitted he was was "stupid and reckless" and had been coming down from smoking crack cocaine and heroin.

He was on his way to sell the stolen car for £300 to buy more drugs when he killed Ms Cooper and Makayah.

He said: "I understand I have caused a lot of hurt and pain. I'm truly sorry for what I've done."

The young man said his life had been "out of control" at the time he was "sofa surfing" with friends.

Mitigating, Tyrone Smith QC told how Dobby had a "fractured upbringing" with time in care and a "principal family member" also an addict.

He asked Dobby: "Do you think you would have committed these offences if you had not been in the grip of drug addiction?"

The defendant, who admitted never owning a driving licence, replied: "No. It was down to drugs that I committed the crimes to fund my habit."

Judge Nicholas Hilliard QC will sentence Dobby later for the two deaths and causing injury to a 13-year-old girl.

Dobby has also admitted dangerous driving relating to an incident on August 26 last year on the A228 near Snodland in Kent.

The Independent Police Complaints Commission is investigating the circumstances of the crash on August 31 last year.