Lucy Beale's killer Bobby Beale played by new actor Eliot Carrington

Lucy Beale's killer was finally revealed in a dramatic and highly anticipated episode of EastEnders on Thursday evening as one of the most gripping "whodunnits" came to an end – almost a year after it began.

Bobby Beale, Lucy's 11-year-old half-brother was unveiled as the culprit during a flashback semi-live episode to mark the 30th anniversary of the popular BBC One show – and the actor playing the youngster was cute brown-haired actor, Eliot Carrington, rather than the blond-haired cherub-looking boy that had previously played the role.

Bobby Beale, played by Eliot Carrington, was revealed as his sister's killer on Thursday

In the episode that had the nation on the edge of the sofa, viewers saw Jane Beale receive a call and rush over to the Beale house where she finds Lucy's body on the floor. Jane then turns to see Bobby standing behind them.

"Whatever she says, she started it. She made everyone unhappy," Bobby says, drawing a close to one of the biggest storylines in the soap's history.

The gripping mystery of Lucy Beale's murder was finally revealed

The twist certainly surprised EastEnders' fans, as did the new actor behind the role of Bobby – 12-year-old Eliot, who has appeared in supernatural comedy-drama Switch as well as Casualty, took on the role of Ian's son on 25 November 2014, and took centre stage in the soap this week.

The revelation of the culprit came after a tumultuous week in which several Walford residents turned on each other as the tension mounted and the mystery slowly unravelled.

Jane Beale, Ian's fourth wife, pictured on the live episode show

This week 's EastEnders Live Week saw regular episodes airing on Tuesday, Wednesday and Thursday interspersed with live scenes, pulling in more than one million extra viewers. Friday’s episode will be the only completely live episode of the week.

Not even the BBC soap's cast members knew who had killed Lucy, played by Hetti Bywater, until the night of the live episode, with Jake Wood, who plays Max Branning, revealing that the actor or actress who plays the killer themselves probably wouldn't find out they've done it until the day.