One of London’s main railway terminuses was plunged into darkness late on Monday when the station lighting failed, causing delays to services.
Paddington Station was illuminated by little more than shop lighting and digital display boards, as station staff used torches to guide passengers.
Network Rail said engineers were trying to identify the cause of the problem, which arose at about 22:00 GMT.
Passengers were advised to check live information before travelling.
Paddington connects South Wales and the West of England to London, serving stations including Reading, Oxford, Cardiff, Exeter St David’s and Penzance.
BBC journalist Patrick Jackson arrived at a gloomier-than-normal station at about 23:15 GMT and said lights above platforms one to four went out about five minutes later.
“It was pretty dark by the platforms,” he said. “It was just a bit weird but there was no panic.
“People just stood there waiting. They didn’t want to bring trains into the station in the dark but we saw two crawling in and we boarded about 20 minutes later.
“The staff just turned on their torches and phones and were directing us towards the carriages.”
Mr Jackson said his Cardiff-bound train left about 20 minutes late.
Shortly after midnight, a Network Rail spokesman told the BBC the problem was affecting services arriving at and departing from Paddington but that the station remained open for overnight travellers.
“We are telling passengers to check before they travel. We have got engineers on site to try to work out the cause and fix the problem,” he added.