Clive Hornby - Emmerdale's flat cap-wearing Jack Sugden - died last night at the age of 63, it was announced today.
Hornby was the longest-serving cast member in Emmerdale's history, a fixture in the soap for 28 years.
His last scenes were broadcast in February, but the star had been determined to beat a mystery illness and return to work.
Emmerdale series producer Anita Turner said: "This is a devastating loss and we are all deeply saddened.
"Clive will be greatly missed by everyone who has worked with him on Emmerdale during the past 28 years.
"He was a hugely popular and well-respected member of the cast and a terrific actor. Our thoughts are with his family at this difficult time."
Hornby first walked on to the Emmerdale set on February 19, 1980, after being offered a three-month contract.
He took over the role from Andrew Burt, who had played Sugden since the first episode.
Recently, the star said of his longevity on the soap: "I can't believe I'm still here sometimes. Some of the kids in the show weren't even born when I started.
"But I love it. I must be a survivor because 28 years is a long time to survive in a soap. I can't imagine leaving".
His character was married three times, had five children, and suffered plenty of on-screen strife.
Despite the changes to the show, originally called Emmerdale Farm, one thing remained consistent for flat cap and wax jacket-wearing Sugden.
"Believe it or not, I still wear the same cap," Hornby recently said, "the one I was given on my first day".
Sugden's first wife Pat was killed off in a car crash in 1986 - the first of many tragedies for his character.
In real life, he went on to marry Helen Weir, who played Pat. They divorced eight years ago and have a son, Tom.
Sugden was one of the soap's favourite characters and started out as a ladies man.
His on-screen dramas have included the death of his second wife in a barn fire, his arrest for her murder before the real culprit was discovered, being shot at by his son and almost being killed in a fire.
Hornby was born and raised in Liverpool and started his working life as an accounts clerk.
In the 1960s he went on to enjoy success as a drummer with pop group The Dennisons.
The band were compared to and played on the same bill as The Beatles at Liverpool's famous Cavern Club and tipped as the next big thing.
When the group split, Hornby turned his attention to acting, attending the London Academy of Music and Dramatic Art before going into repertory theatre.
He also appeared in army sitcom Get Some In!, Gerry Anderson's Space 1999 and Minder alongside George Cole.