The victim was found stabbed near the entrance of Norbury Park in Courtlands Avenue
One of the attackers is believed to have been carrying a hand gun which he used to hit the victim.
The victim required surgery due to the injuries he sustained.
“I would urge anyone who has any information to contact police; your call could prevent another attack or even save a life.
“We are determined to bring those responsible to justice and we asking the community to do all they can to assist us.”
Scotland Yard is appealing for witnesses
“There have been no arrests and enquiries continue.”