London’s passenger watchdog has called for an investigation after thousand of people were trapped on trains on Thursday evening when power lines were damaged. Passengers, who were given little information during the ordeal, were stuck for more than three hours on dark, cold trains – including on Elizabeth line trains, which have no toilets and rely on the overhead lines for power. Around seven trains were stranded, operated by the Elizabeth line, Heathrow Express and Great Western Railway (GWR). Damage to the overhead lines in the west of London caused severe disruption that was set to last into Friday evening. The watchdog, London TravelWatch, said an investigation was needed and expressed concern over the “lack of communication and slow response time” after the stoppages. The incident occurred during a 24-hour strike by train drivers in the Aslef union on GWR and Heathrow Express services. It is understood that the GWR train caught in the damaged wire was being driven by a manager while regular drivers were on strike. Most companies around England have not attempted to run any trains during this week’s rolling strikes. Network Rail said on Thursday that the problem was caused by a train striking an “obstruction between Paddington and Acton mainline”, causing damage to the overhead wires. Transport for London said in a statement: “We’re sorry that the damage caused to Network Rail’s overhead power lines by another rail operator’s train has caused significant disruption to our Elizabeth line customers as well as all train operators out of London Paddington. We worked to get customers off stranded trains as quickly as possible and to provide any support needed.” A spokesperson for Aslef said: “Some train companies choose, quite sensibly, to take the practical decision to suspend all services on strike days.” According to Aslef, the driver of the GWR train that ended up caught in the wire usually worked as an operations investigations manager. The spokesperson added: “I suppose, as an operations investigations manager, he is uniquely qualified to investigate … what went wrong.” A GWR spokesperson said: “The only people who can drive our trains are competent train drivers, properly qualified with appropriate route knowledge. As yet, there is no evidence that the overhead line equipment fault was due to a train.” The singer James Blunt, and the TV presenter Rachel Riley, were among the passengers caught up in the disruption on Thursday. Blunt posted on X: “Been stuck somewhere outside Paddington for close to 4 hours now. Out of peanuts and wine,” while Riley wrote: “Nearly 4 hours after we got on, we’re getting off the Elizabeth line, woohoo!” Network Rail’s own chief executive, Andrew Haines, was also on board one of the stranded trains, which he said was a “painful experience”. In a message to staff, he wrote that railways had “gone backwards on customer service”. He told them: “As an industry, we let down thousands of passengers after a hugely disruptive incident just outside of Paddington station.” Haines said it was not yet “the place to go into the whys and wherefores – the causes of the incident are yet to be determined”.