The first sign of trouble Peter Hughes noticed was when his train to Madrid started to slow down.
Then the TV monitor and lights went off. Emergency lights switched on, but did not last, and the locomotive ground to a halt.
Four hours later, Mr Hughes was still stuck on the train 200 kilometres (124 miles) outside of Spain's capital. He had food and water, but the toilets were not working.
"It will be getting dark soon and we could be stuck here for hours," he told the BBC.
The massive power cut that stranded Mr Hughes triggered chaos across Spain and Portugal, and also impacted Andorra and parts of France, from about midday local time (10:00 GMT).
Traffic lights shut off. Metros closed. Businesses shuttered and people joined queues to get cash as card payments did not work.
Jonathan Emery was on a different train halfway between Seville and Madrid when the cuts hit.
For an hour, he sat on the train, the doors closed, until people could pry them open to let in ventilation. Half an hour later, passengers left, only to find themselves stranded.
That was when people from local villages started coming and dropping off supplies – water, bread, fruit.
"Nobody is charging for anything, and word must be getting around in the local town because people just keep coming," he said.
Commuters in Madrid were left confused in the dark when the blackout hit the city's metro station network. One resident, Sarah Jovovich, was getting off the train when the lights went out.
People were "hysterical" and "panicking", she told the BBC. "It was quite chaotic really."
Mobile phones had stopped working and nobody had any information. Once out of the metro station, she found the roads gridlocked with heavy traffic.
"No-one understood anything. Businesses were closed and buses were full," she said.
Hannah Lowney was halfway through scanning her grocery shopping at Aldi when the power went out in the Spanish capital.
People were coming out of their offices and walking home because they could not tell when the buses were coming, Ms Lowney said in a voice message sent to BBC Radio 5 Live.
"It's a bit disconcerting that it's the whole country, I've never experienced this before," she said.
Mark England was eating lunch in the restaurant of the hotel where he is staying on holiday in Benidorm when "everything went off and the fire alarm started going off and the fire doors started closing".
In an international school in Lisbon, the electricity flickered on and off for a while, then gave up, teacher Emily Thorowgood said.
She kept teaching in the dark, the children in good spirits, but lots of parents were taking their children out of school, she said.
Will David, a Brit living in Lisbon, was having a haircut and beard trim in the basement of a barber when the power went down. The barber found him a spot by the window upstairs to finish the cut with scissors.
"The walk home felt very strange, both with the lack of traffic lights meaning a complete free-for-all for vehicles and pedestrians on the roads - as well as so many people milling around outside their places of work with nothing to do," he said.
Initially, mobile phone networks also went down for some, leaving many scrambling for information.
Curtis Gladden, who is in La Vall D'Uixo, about 30 miles from Valencia, said it was "scary" as he struggled to get updates about what was happening.
Eloise Edgington, who could not do any work as a copywriter in Barcelona, said she was only receiving occasional messages, could not load web pages on her phone and was trying to conserve her battery.
