Seymour Gerald. The Outsiders

They used to meet for a smoke behind the MI5 building. They were disbanded after the death of the youngest member of their team at the hands of a Russian gangster. Now, suddenly, the Graveyard Team is being called back together.
Word is that the gangster is staying at a villa in Spain - the Costa del Sol being a multi-billion dollar hub in the worldwide drug trade.
Winnie Monks has never forgotten - or forgiven - the murder of her agent. Now she asks permission to put a photo surveillance unit in the empty house next door to the villa, not mentioning that she is also sending one of the Graveyard Team - Sparky the sniper.