Boris Johnson said “absolutely everything” is being done to tackle violent crime, after a mother and former Conservative Party activist pleaded with him for help following her only son’s stabbing death.

Sven Badzak, a 22-year-old aspiring lawyer from Maida Hill, west London, was killed and his friend is fighting for his life after they were chased and attacked by a group in Kilburn, north-west London, at around 5.30pm on Saturday, Scotland Yard said.

His mother, Jasna Badzak, told of her devastation at the loss of her “beloved” son in what she believes was a random attack.

She told the PA news agency: “I can’t believe it’s happening to me, that it happened to my child who was so, so far away from any of those kind of things (violence). I just can’t believe this is actually happening.”

Ms Badzak said her son had gone to a shop to get orange juice and then to a bagel shop when he was attacked.

“He was waiting for the bagel to be done,” she said. “He was just attacked for no reason.”

She added: “He was beloved by everyone.”

Ms Badzak said her son, who had a degree in sociology but wanted to become a lawyer, had met the Prime Minister and other well-known Conservative politicians when he was younger, through her campaigning work with the party.

Asked what she would say to Mr Johnson, she said: “This is a child and his mother who helped you get elected. You knew Sven. You were high-fiving him as your mate.

“I want to hear from him (Boris Johnson), from (David) Cameron, from (George) Osborne.

She added: “I just want the Prime Minister to tell the police to do their job, catch the perpetrators, get the evidence beyond any doubt and convict them.”

I think that what's happening on the streets of too many of our cities is very, very sad

Mr Johnson said his thoughts are with Ms Badzak and her family “in mourning the loss of her son”.

He told reporters: “I think that what’s happening on the streets of too many of our cities is very, very sad and I want to see kids protected from some of the gang crime, the knife crime, the culture of violence that they’re all too often sucked up in.”

He said he is concerned there could be a “rebounding” in crime figures as the country emerges from lockdown, and said efforts are being made to ensure a “tough policing policy response” and also to “make sure that kids, young people, have other things to do, they don’t get sucked into the nihilistic culture of these gangs”.

He said there has been “some success” on that front, but added: “That’s no consolation, I know, to a grieving mother, but we are doing absolutely everything we can to fight those gangs.”

Police have described the attack as “barbaric” and said they believe “Sven and his friend became involved in an altercation with a group of males”.

Mr Badzak, who was privately educated at Wetherby and Portland Place schools before attending Roehampton University, would not have become involved in an “altercation”, his mother said.

Ms Badzak, a consultant and financial analyst, said: “There was no altercation, they were attacked for no reason whatsoever.”

She urged anyone with information about what happened to come forward.

She added that she has not yet seen her son’s body and wants to be able to do so soon.

Lead detective Chief Inspector Darren Jones, of the Metropolitan Police, said: “As this group chased the pair, Sven and his friend became separated.

“Sven fell to the ground and was attacked by a number of the group.

“His friend was also attacked but managed to seek sanctuary in a shop; however, he remains critically ill in hospital.”

Mr Jones said police will support the families through their investigation and that a “team of highly experienced officers will be working tirelessly to locate and apprehend those responsible for this horrific attack”.