A landmark pub came within two minutes of being burnt to the ground after a customer innocently put out a cigarette in a hanging flower basket.
The butt slowly ignited the soil in the basket that, 11 hours later, caused a blaze to break out in the Chester Bar and Restaurant on the Antrim Road.
Three fire appliances rushed to the scene in the middle of the night to tackle the inferno, which has closed the pub's restaurant and function room.
General manager Gerard Quinn said: "The Fire Service said we came within two minutes of the whole roof catching fire and the premises being razed to the ground.
"It's scary to think that an unwitting act of carelessness by a member of the public could have had such devastating consequences. The Chester could have been destroyed and 35 staff put on the dole because a customer didn't use an ashtray."
Mr Quinn said he raced to the premises when alerted about the blaze shortly after 5am on Monday. "I couldn't believe my eyes, there were flames shooting into the sky and they were trying to bring them under control.
"At first I thought it was arson. We had put several guys out of the pub recently, and I suspected it might be linked to that. It was only after going back through CCTV footage that we saw it had all started with a cigarette butt in the flower basket."
The bar had provided ceramic ashtrays and stainless steels ones attached to the wall, but in this incident they weren't used.
At 6.15pm last Sunday a woman put out a cigarette in a hanging flower basket in an outside smoking area adjoining the pub's function room.
A few minutes later a man noticed that the butt was smouldering and removed it. One guest pours beer into the basket to dampen it down. However, another guest then appears to extinguish his cigarette in the flower basket.
Mr Quinn said: "CCTV footage shows a very small flame appearing in the basket about 9pm."
He said he believed the butt had ignited the peat moss, and it had smouldered for three hours.
"It burns slowly until just before 5am," he said.
"Then the whole basket becomes a ball of flames and a gust of wind blows some of the burning peat onto the wooden decking. The roof of the restaurant below the smoking area then catches fire."
Staff at the Ambassador Nursing Home next door noticed the blaze and dialled 999. At the same time, the Chester's own alarm went off. "The Fire Service arrived within two-and-a-half minutes of being called," Mr Quinn said.
"Their promptness and professionalism - as well as the vigilance of the nursing home staff - saved this pub.
"I'm more than a wee bit emotional about it. I've worked here 25 years and my father worked here before me. The Chester is part and parcel the local community."
He said that lessons must be learned.
"The message for other establishments is that a cigarette butt can turn a flower basket into a fire hazard, and it must be stressed to customers to use the ashtrays provided," he added.
A Fire Service spokesman said crews had been at the scene for over three hours and the blaze was being treated as accidental.
"Firefighters wearing breathing apparatus and using hose-reel jets, covering jets and thermal imaging cameras, dealt with a fire on the first floor of the premises.
"We would remind everyone to fully extinguish all smoking materials after use," he said.