A former train driver who crashed into scaffolding, with breath that smelt "slightly" of alcohol, has been found guilty of being unfit for work.

Joseph McKeraghan, of Raynes Park, was found guilty on Monday of being unfit to work because of alcohol or drugs, while on duty at Selhurst Traincare Depot on December 27, 2018.

McKeraghan, 59, had pleaded not guilty to the charge.

McKeraghan, who has since resigned, did not appear at Westminster Magistrates' Court, where he had been due to represent himself.

A warrant has been issued for his sentencing.

McKeraghan was on duty from 3.30pm, when about half an hour into his shift he hit some scaffolding ladders, which were then dragged under the train, the court heard.

David Harris, who was an engineer on duty at the time, was sent to the scene, and said there was a "slight smell" of alcohol on McKeraghan's breath.

"There was a not very strong, but a slight smell, of alcohol," Mr Harris told the court.

"He didn't seem intoxicated, he wasn't slurring, he was very helpful.

"The best I could explain it as, is a day-after smell."

McKeraghan helped clear the area before saying he was going to wash his hands, the court heard.

"I assumed he was just going to wash his hands," Mr Harris said. "Later in the evening, I found out he had gone."

The court heard that when McKeraghan was called to attend the depot office to give a statement, he could not be found or contacted.

British Transport Police were then alerted.

Inspector Michael Tanner went to McKeraghan's house and found him in his work uniform holding a bottle of wine.

"When he opened the door I could smell alcoholic liquor on his breath as he was speaking to me," Mr Tanner told the court.

"He seemed unsteady on his feet and his eyes were glazed."

McKeraghan was arrested and samples of his breath were taken at 9.50pm, five hours after the collision.

The lowest reading recorded 38 micrograms of alcohol in his system.

Mr Tanner said McKeraghan claimed he started drinking the bottle of wine after the collision at 7.30pm.

The officer added that while there was some wine in the bottle, McKeraghan had drunk "most" of it.

The alcohol limit for train drivers is 13 micrograms, the court heard.

Forensic scientist Michael Robinson analysed McKeraghan's alcohol level to determine if it was consistent with the wine he claimed to have drunk after the collision.

He found the amount of alcohol McKeraghan claimed to have consumed was not consistent with his recorded blood alcohol level.

Mr Robinson said McKeraghan's blood alcohol level at the time of the reading would have likely been between 13 and 81, with a most likely level of 44.

"I know he said he didn't drink anything before the incident, I'm saying in my opinion he has drunk more," Mr Robinson told the court.

Finding McKeraghan guilty, chairman of the magistrates Mr Jeffrey Manton said the bench was "certain" he was unfit for work at the time of the collision.

Mr Manton added that it was "disappointing" McKeraghan did not attend court. "It's very disappointing because we could have heard that side as well," he said.