LONDON ? EastEnders, one of Britain's longest-running soap operas, celebrated its 25th anniversary on Friday with a first live episode, revealing the answer to a wide-ranging whodunit.

The hugely popular show, screened on the BBC's overseas channels and sold around the world, is set in the fictional Albert Square in east London where conflict is seemingly never far away.

To mark its quarter century, producers finally revealed who killed the Archie Mitchell ? a scheming villain from one of the show's main families ? in the Queen Victoria pub on Christmas Day.

He was bludgeoned with the bust of the pub's royal namesake, which has sat on the bar for 25 years.

Even the actors were kept in the dark until the last moment: scriptwriters wrote 10 different endings, the real one revealed to the cast only half an hour before showtime.

Young bride Stacey Branning ? raped by Mitchell ? admitted the killing in the show's final seconds after her husband fell to his death off the pub's roof.

Bookmakers had put her volatile brother Sean as the chief suspect ? even though he had been out of the show for more than a year. Paddy Power had Branning as a 14/1 11th favorite.

Friday's one-off episode used 36 camera operators rather than the usual four. Background clocks were set to real time. The show featured tears, mobile phones ringing on cue, a rooftop police chase, an old video featuring characters from the early years, and only the occasional camera wobble.

The soap was launched in 1985 and soon earned a large following. Viewing figures peaked during Christmas 1986 when 30 million people ? more than half the population ? watched "Dirty" Den Watts hand a divorce letter to his wife Angie.

The soap, which airs four half-hour episodes per week, pulls in around 10 million British fans nowadays, but a surge in viewing figures was expected for the live episode.

The show has tackled many social issues over the years, including the HIV virus, teenage mothers, rape, drug addiction, incest, assisted suicide and child abuse.