By Michael Osborn BBC News entertainment reporter

Steph and Shelley have a final fight in the landmark episode

The 4,000th epsiode of long-running soap Emmerdale on Thursday will be marked with a deadly showdown between two bitterly-opposed characters.

It is a far cry from the first edition in 1972, when Emmerdale Farm was a dour saga about the lives of farming folk tucked away in the daytime schedules.

By the late 1980s, the farm had been eased out of the spotlight in favour of a village of wider-ranging characters, and Emmerdale staked its place in ITV's prized peak-time evening slot.

Plane crash

From 2003, it became the only British soap to air six episodes per week, including Sundays.

Emmerdale made headlines and huge ratings in 1994 when a plane crash devastated the village and cut a swathe through the cast list, giving the soap a more youthful, dynamic and dramatic feel.

Thursday night's hour-long special could see the last stand of psycopathic Steph - who drugged and imprisoned her own father - and is likely to land EastEnders with another ratings headache.

EMMERDALE TRIVIA Emmerdale is also shown in Canada, Ireland, New Zealand, Bulgaria and Scandinavia Soap stars who started in the show include Pam St Clement, Ross Kemp and Anna Friel The only remaining original cast member is Jack Sudgen - but he has been played by different actors There have been 35 Emmerdale weddings - and one lesbian blessing

Emmerdale has managed to beat its rival on numerous occasions, most recently when village siren Charity Tate made her exit from the soap after five turbulent years.

A succession of strong women is just one of the ingredients that gives the Yorkshire-based soap its appeal, according to Inside Soap magazine's editor Steven Murphy.

He says the mould was made by scheming Kim Tate, whose feats from 1989-99 included a return from the dead, the shock of which sent her husband to an early grave.

She used her make-up compact to check he had stopped breathing, and then touched up her lipstick - a moment Mr Murphy rates among his Emmerdale favourites.

Uniqueness

He adds that the show has a formula which is unique among soaps and has won it many fans.

"It's about the struggle between the haves and have-nots. There are the people in the big house with the money, and those in the village without it.

"These sometimes cross - as they did recently with Charity and business magnate Tom King - and this great class structure gives Emmerdale its uniqueness," says Mr Murphy.

Emmerdale was laid waste by a huge plane crash in 1994

Actress Patsy Kensit is the latest well-off Emmerdale resident to create havoc in her wake, while the sprawling Dingle clan have enjoyed moments of comedy and drama for more than a decade.

The original Emmerdale Farm may be lost in the mists of time, but its first matriarch Annie Sugden, now retired in the Spanish sunshine, still merits the odd mention.

Steven Murphy says that all soap operas have their peaks and troughs, but feels that Emmerdale has been ahead of the game for some years now.

Homosexuality, schizophrenia and killer storms have been at the centre of just some of the soap's recent storylines.

"It's the most consistent soap with a good balance of humour and drama, and they're always sowing the seeds of new characters," he says.

"Emmerdale is here to stay. It's the lynchpin of ITV's schedule and if they do it as well as they have been, there's no reason why it shouldn't make future milestones," adds Mr Murphy.