Long-running soap EastEnders will finally reveal how its character Lucy Beale was killed in a flashback episode as part of the show's 30th anniversary week.

The episode, to be screened on BBC One next month, will bring an end to the "whodunnit" story which has gripped viewers since Ian Beale's daughter was murdered on Good Friday last year.

An EastEnders spokeswoman said the episode would take viewers back to the night of the killing and "fill in the blanks" surrounding the storyline.

Fans will not only learn how Lucy met her death but also why the murder was carried out, she added.

Several cast members will reprise their roles, including Hetti Bywater, who plays Lucy Beale, Jamie Lomas as bad boy Jake Stone and Tanya Franks as blackmailing prostitute Rainie Cross.

EastEnders, which was first broadcast on February 19 1985, will celebrate 30 years on air with a "live" week from Monday, February 16.

It will include a 30-minute live show and "live elements" in the remaining episodes that week.

EastEnders executive producer Dominic Treadwell-Collins said: "When we first created the Who Killed Lucy Beale storyline, we knew that we had to flashback to the night that she died on screen.

"So much happened on Good Friday 2014 after viewers saw Lucy leave her home and walk off into the night - and this Flashback episode will fill in the pieces for the rest of that night, before she was killed.

"This also gives us the opportunity to have some fun with other characters, with new twists appearing in old storylines as secrets from the year before are revealed.

"With the added live element for some scenes, this is going to be an extremely special episode and the pearl within our week of celebratory episodes for EastEnders' 30th birthday. "

During the 30th anniversary week, Ian Beale is set to marry ex-wife Jane and actress Barbara Windsor will reprise her role as feisty barmaid Peggy Mitchell for one episode.