The teenager who killed pensioner Richard Mannington Bowes during the summer riots has been sentenced to eight years' detention.
Darrell Desuze, 17, punched the elderly man to the ground on 8 August last year as disturbances swept the country.
Bowes, who had been trying to put out a fire in a dustbin near his home in Ealing, west London, suffered brain damage and died three days later in hospital.
Desuze's mother, Lavinia, was jailed for 18 months at the same court for perverting the course of justice by cutting up her son's clothes. Desuze, who could be named after a judge lifted an order banning his identification, admitted manslaughter last month.
Passing sentence on Tuesday, Mr Justice Saunders said he took into account the teenager's previous guilty pleas to violent disorder and burglary at William Hill, Tesco Express, Blockbusters and Fatboys Thai restaurant on 8 August.
He said Desuze "played a full part in the violence" and could be seen on CCTV smashing windows, looting shops, throwing missiles at police and wheeling rubbish bins into the street so they could be set alight. He said most people were afraid to go out, and those caught up in the violence would have been "terrified".
"One person who was not terrified to be out and was not prepared to be forced off the streets was Richard Mannington Bowes."
He said CCTV footage showed the pensioner moving among the riots and trying to prevent bin fires from spreading.
"The death of Mr Bowes was pointless and unnecessary and it became for the public one of the most, if not the most, shocking event of the riots in London," he said.
Desuze ? who once watched officers being pelted with bricks during a simulated riot on a school trip to the Metropolitan police riot training centre in Gravesend, Kent ? was caught on camera kicking in the glass doors of a shopping centre before joining a mob that attacked heavily outnumbered police with missiles around Spring Bridge Road.
Wearing sunglasses and a top saying "Robbers and Villains", he threw his full weight behind a punch to Bowes's jaw, buckling his legs and knocking him unconscious.
The pensioner fell backwards on to the pavement, his head taking the full force of the impact.
Prosecutors said police were "simply unable to reach Mr Bowes for some minutes because of the violence against them".
In a victim impact statement read to the court, Bowes's sister Anne Wilderspin, who was in court, said she forgave Desuze, repeating what she said just after her brother's death.
"Richard was my only brother and although I have been separated from him for many years, I had always hoped to be reconciled with him again," she said.
"When I heard that he had been injured in the Ealing riots, I was hoping that my long-held desire to see and talk to him was being fulfilled."
She said she was disappointed when she arrived at hospital in Paddington to find he had not regained consciousness and was on a life-support machine.
"I was completely devastated that I had found my brother and lost him again on the same day," she said.
But she said she was concerned for the accused and felt compassion for him. "He has potentially ruined his life and will find it difficult to make an honest living in the future."
She said he had committed a "terrible crime" but added: "I do forgive him and, as a committed Christian, pray to the Lord Jesus that he will turn over a new leaf. Both my husband and I hope that in this case justice will be tempered with mercy."
She said she hoped the teenager would be rehabilitated in a "loving environment and find a new purpose in life".
The judge said that on 13 August Lavinia Desuze cut up her son's clothing and took it to two litter bins at midnight.
She later admitted to police what she had done, the court heard.
"I do feel, as most people would, some sympathy for Lavinia Desuze," the judge said.
"On the jury's verdict, even though she committed a very serious offence, she did so to protect her young son to whom she had given birth when she was only 14 and who she had looked after as a single mother for most of his life ? I accept that the instinct of a mother to protect her child is a very powerful one."