THE entrance is up a short Glasgow wynd where my sudden appearance disturbs a couple eating pies.

They presumably did not feel it was correct to eat meat and pastry in full view of the shoppers hurrying along busy Argyle Street just a few steps away, and had sought a quieter eating area.

After a short flight of stairs I am in a music hall, the ceiling still brown from generations of smokers from an era when indoor smoking was almost compulsory. In fact this music hall did not even have an indoor toilet for its first half century, and the fanciful claim is that the floor being quietly soaked by years of urine from audience members caught short saved the wooden structure from being burned down from accidentally dropped lights.

On stage the Master of Ceremonies is being cheekily dismissive of the acts, describing one singer as having "performed all over the Empire - the Empire Bar in Saltmarket." This is, after all, the music hall where the phrase "no turn left un-stoned" was coined.

This really is a time warp. I'm in the Britannia Panopticon, said to be the world's oldest surviving music hall, hidden in full view of the public on Glasgow's Trongate above an amusement arcade, but boarded up and unloved for much of the last century.

A charitable trust, led by a fizzingly enthusiastic Judith Bowers, who fell in love with the Panopticon when she persuaded the amusement arcade owners to let her peek inside, continues to fundraise to preserve it. But what's the point of a music hall without music? For the next four years the hall will have an exhibition of the First World War, tracing its bloody unfolding in real time, as well as a once-a-month show of performers recreating the music hall of the time.

For it was in music halls that the public 100 years ago learned how the war was progressing. Peppered among the musical acts would be the first newsreels showing black and white film of what was happening at the Front while people led their normal lives back in Glasgow. For this was different from the Second World War. There were virtually no air raids, and so the civilian population was left untouched, only finding out through the newsreels of how horrific modern warfare had become.

The inside of the Panopticon is untouched so you are sitting there in the same surroundings as the audiences a century ago, but fortunately without the crude toilet use, or smoking. The moving show replicates the jaunty upbeat style of the early army recruiters before a more stark telling of the pointless death and maiming follows. Plus songs of course.

Judith Bowers is on stage - didn't I tell you she was enthusiastic - wearing a fake moustache, and dressed in pyjamas and dressing gown to sing the music hall song A Bit of a Blighty One about a soldier injured by a splinter and lapping up the attention of the nurses. "When they mop my brow with sponges, And they feed me on blancmanges, Oh, I'm glad I've got this bit of a blighty one," she croons.

Fortunately the audience at the weekend was far more appreciative and sedate than the earlier audiences at the Panopticon when it opened as the Britannia Music Hall in 1857.

As Judith explains, Glasgow was bursting at the seams then with thousands of factory and mill workers living in the worst conditions imaginable. "Men, women and children toiled in the most atrocious and dangerous conditions" she says. "The stench of the sewers, the thick smoke that belched from the factories and mills making the air foul to breathe, and the lack of plumbing would be insufferable to our modern dispositions - only the strongest survived.

"The audience comprised 1500 of these people, who would cram into the small auditorium four times a day, squeezing up on the rough wooden benches to be entertained, blow off steam, have a laugh, and escape from their difficult lives."

It's said folk would pick up horse manure outside to keep their hands warm and then fling it at acts that dissatisfied them. Stan Laurel performed here for the first time as a schoolboy. Legend has it that his first joke was about two butterflies discussing a dance they had gone to, but one had not enjoyed it as it had been "a moth ball". Gosh, it's so old it might have appeared in The Diary.

Film star Cary Grant appeared under his own name Archie Leach as a dancing stilt-walker. Hollywood must have seemed a breeze after that.

For Judith, the urge to preserve the Panopticon is as a memorial to these thousands of early Glaswegians who would have gone to paupers' graves and have no other reminder that they ever existed.

As the Britannia Music Hall it eventually became dated, and was taken over by showman AE Pickard who grandiosely renamed it the Panopticon, from the Greek, to see everything, as he added a zoo in the basement and a freak show and a carnival on the roof. But by the Second World War it could not compete with modern cinemas and variety theatres and closed, with its original ceiling and walls boarded up to make way for, at first, a chicken farm, and then a tailor's factory before it closed altogether.

Now the Friends of the Panopticon, the usual cheery bunch of eccentrics and hard-workers who get involved in such projects, strive to keep it going. Government grants have been secured to refurbish the building bit by bit. But the tobacco-stained ceiling will remain, says Judith. That's also part of Glasgow's colourful history.