"GREEN door, what's that secret you're keepin?" asked Shakin' Stevens on Top of the Pops in 1981.
Now, 25 years after it hit No 1, Wales on Sunday can reveal exactly what was behind the mysterious door - a gay club!
A new report written by a university academic reveals the green door was real and hid a secret lesbian bar off London's trendy King's Road.
The members' only bar, on Bramerton Street was one of Britain's first for lesbians, and was known to its regulars as the Gateways.
Rebecca Jennings of Manchester University investigated the bar for her article The Gateways club and the Emergence of a Post-Second World War Lesbian Subculture, which appears in the journal Social History.
And she discovered it provided the inspiration for the Shaky anthem - originally a hit in 1956 for Frankie Vaughan - and it turned out to be a song about a man trying to get into a lesbian bar.
The secret watering hole explains the lyrics belted out by Shaky: "There's an old piano and they play it hot behind the green door, don't know what they're doing but they laugh a lot behind the green door.
"Wish they'd let me in so I could find out what's behind the green door."
The line "Joe sent me" is believed to refer to Joe Meek, the gay record producer who worked on the original. He was an honorary member of the bar.
"When I said, 'Joe sent me', someone laughed out loud behind the green door," complained Shaky.
The inside of the club was only ever filmed once in a 1968 film called The Killing of Sister George. Fifteen minutes of the movie was shot in the Gateways with many of the regulars appearing as extras.
The club shut its green door in 1985 and is now storage space for a nearby dress shop.
Justin Rigby, Shaky's agent, said he did not think Shaky knew what he had been singing about for the past 25 years.
"I haven't got a clue to be honest, but it wouldn't surprise me if it's true," he said.
"It wouldn't amaze me. A lot of songs have hidden meanings - what with the reprobates most singers and songwriters are, nothing surprises me.
"I don't think Shaky ever knew that, though."