A depot train driver accused of being under the influence of alcohol when he crashed into scaffolding went home after the collision and drank "most" of a bottle of wine, a court has heard.

Joseph McKeraghan, of Raynes Park, is charged with being unfit to work because of alcohol or drugs at Selhurst Traincare Depot in Croydon on December 27, 2018.

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

He did not appear at Westminster Magistrates' Court on Monday, where he was due to represent himself.

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 inspect and said there was a "slight smell" of alcohol from 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 after the collision, he could not be found or contacted.

The British Transport Police was then alerted.

Inspector Michael Tanner went to McKeraghan's house and allegedly found the accused 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.

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.

The trial in front of Magistrate Chair Jeffrey Manton continues.