The murder of a man in north London has been linked to a knife attack on the same night, new DNA evidence has shown.
Ricky Smith was fatally stabbed in the chest in Hamilton Road as he walked home in Highbury Park with his partner, on 3 October 1997.
The Met Police has revealed new analysis of clothing found near the scene linked the case to an attack in Harlesden two hours earlier.
Both incidents were unprovoked attacks, the Met said.
A man approached and stabbed Mr Smith, a father-of-two, as he walked home after a night out with his partner.
Police believe the attacker fled the scene on foot up to Conewood Street, where officers found a blue baseball cap, a jacket with the wording 'Chicago Bulls' and a five-inch lock knife with a £9.95 price sticker on it.
Two carrier bags were also found at the scene.
Forensic analysis of the items revealed the link to the stabbing of a 21-year-old man in College Road, Harlesden, at about 21:15 BST.
The victim, Juan Marais, now 35, said he was stabbed in the chest and abdomen by a man who asked for the time.
The attacker then took his carrier bag, containing cans of beer, police said.
The suspect in both attacks has been described as a tall black man aged between 18 and 30 years.
Det Insp Colette Smyth said: "The suspect did not utter a word before producing a knife and stabbing Ricky in the chest.
"Following forensic advancement we are now able to officially link Ricky's murder to a serious stabbing in Harlesden.
"We urge anyone who has information about either incident to come forward no matter how insignificant they think it might be."
Mr Smith's father, Keith, said: "Our grandchildren have grown up without their dad and we want to know why this has happened.
"He didn't deserve to have his life taken away."
The force said that the day after the attacks, a man made inquiries with people in the area about the discarded items.