A £20,000 reward is being offered to catch the killer of two men shot in an apparent case of mistaken identity.
Police have released an e-fit of the gunman
Michael McCormack, 59, and John Ogden, 34, were both shot in the head outside The Sandwich Shop in Cavendish Road, Balham, south-west London, in 1994.
Appealing on BBC Crimewatch, police said the gunman was inside the shop and followed his victims outside before shooting them from behind.
The killer escaped in a white Vauxhall Cavalier, registration D880 MYG.
Mr McCormack, of Ewell, Surrey, and Mr Ogden, from New Malden, south-west London, both worked at the Indexing Company in Balham.
Police say inquiries have revealed no likely motive for their murders, which happened at about 1410 GMT on 21 October, and they believe it was a case of mistaken identity.
It is understood the killer waited for his victims inside the sandwich shop then followed them outside, shot them, and ran off into Weir Road.
The gunman's car was later found burnt out in Rosendale Road at the junction with Norwood Road in Herne Hill, south east London.
Detective Chief Inspector Stuart Cundy, said: "We now have a substantial reward on offer and hoping that someone who has inside information will come forward."