London Underground Power Outage: Cau e and Affected Line

A brief power outage on 12 May 2025 brought five London Underground lines to a standstill, exposing the network’s vulnerability to even momentary grid faults. Thousands of commuters faced hours of disruption after the incident struck just after lunch.

Lines affected: 5 (Bakerloo, Jubilee, Northern, Piccadilly, Elizabeth line) ·
Date of incident: 12 May 2025 ·
Source: BBC News, Sky News ·
Stations closed as of reporting: Embankment and Putney Bridge (later reopened) ·
Duration of major disruption: Several hours

Five key facts at a glance, drawn from verified reports by TfL, ITV News, and Xinhua.

What caused the power outage in the London Underground?

Official cause from reports

A brief interruption of the power supply caused several London Underground lines to lose power on 12 May 2025, Transport for London (TfL, London’s transport authority) confirmed via Xinhua. The outage occurred at about 2:30 p.m. and led to immediate suspensions on the Bakerloo line and severe delays on four others – the Jubilee, Northern, Piccadilly, and Elizabeth line, according to ITV News (UK broadcaster).

Fault on the high voltage network

National Grid (UK electricity transmission network operator) said the fault was on its transmission network in central London and was resolved within seconds. However, the consequent voltage dip likely affected low-voltage distribution supplies in the area, causing the Tube’s fourth-rail system to drop out. ITV News reported that TfL stated “everything shut down” because of a “National Grid issue.” Meanwhile, the London Fire Brigade said three metres of high-voltage cabling were destroyed, and firefighters brought a small fire under control, according to Xinhua.

The implication: even a momentary grid fault can cascade into citywide disruption.

Does the London Underground run on electricity?

Electric traction system of the London Underground

Yes – the London Underground uses a 630-volt DC fourth-rail system to power its trains, according to Wikipedia. Unlike mainline railways that often use overhead wires, the Tube draws current from a live rail (the third rail) and returns it through a separate fourth rail. This design makes the network particularly sensitive to power disturbances from the grid.

Third rail power supply

The power supply originates from the National Grid’s high-voltage transmission network, then is stepped down at substations to the 630V DC used by the trains. When a fault on the 132kV or 400kV grid causes a voltage drop – even momentarily – the signalling and train control systems can trip, leading to emergency brakes and service suspensions. That is precisely what happened on 12 May, as confirmed by KSAT, which reported that trains were stopped temporarily because it was not safe to operate without power.

The takeaway: the Underground is only as reliable as the external power feed. A fault on the high-voltage grid, even if the supply is restored in seconds, can cascade into hours of delays for millions of passengers.

Are London Underground trains running?

Live status from TfL

TfL’s official status page provides real-time updates for all lines. On 12 May, the Bakerloo line was suspended completely, while the Jubilee, Northern, Piccadilly, and Elizabeth line suffered severe delays or partial suspensions, according to ITV News. Overground lines were not affected.

Lines affected on May 12, 2025

• Bakerloo line – fully suspended (ITV News)
• Jubilee line – severe delays (ITV News)
• Northern line – severe delays (ITV News)
• Piccadilly line – severe delays (ITV News)
• Elizabeth line – severe delays (ITV News)

Two stations – Embankment and Putney Bridge – were closed because it was not safe to operate without power, as reported by KSAT. Both reopened later that afternoon.

The pattern: a single point of failure in the grid can cripple the capital’s most vital transport artery.

How long was the 2003 blackout?

The Northeast blackout of 2003 affected approximately 55 million people in the United States and Canada on 14 August 2003. The power outage lasted up to four days in some areas, caused by a software bug in the alarm system at a control room in Ohio. That event was on a far larger scale than the London Underground incident, but both underscore the vulnerability of interconnected power systems.

Why do Tube drivers want a 32 hour week?

In recent pay disputes, some Tube drivers have called for a four-day week (32 hours) as part of negotiations over working conditions and salary. The demand is linked to ongoing strikes and FOI requests that revealed senior drivers can earn up to £70,000 a year, sparking comparisons with airline pilots. TfL has not publicly committed to such a change.

Do Tube drivers earn more than pilots?

According to data from TfL FOI responses, senior London Underground drivers can earn around £70,000 annually including overtime, which is higher than the starting salary for many airline pilots but below experienced captains. The comparison often emerges in public debates about public sector pay and strike negotiations.

Timeline of the London Underground power outage

Three key events mark the May 12 outage, based on verified reports from ITV News, Xinhua, and KSAT.

Bottom line: The outage itself lasted only minutes, but the knock-on delays continued for hours. TfL and National Grid are investigating the cable fault, while commuters face lingering uncertainty about when full service will return.

What’s confirmed and what’s still unclear

What this means: despite many verified details, key questions about cause and future prevention remain unanswered.

What people are saying

“[TfL said] a brief interruption of the power supply caused several London Underground lines to lose power.”

— Transport for London (TfL), as reported by Xinhua

“The fault was on [National Grid’s] transmission network in central London and was resolved within seconds.”

— National Grid, as reported by ITV News

Summary

For London commuters, the 12 May power outage is a stark reminder of the network’s vulnerability: a single cable fault can shut down half a dozen lines for hours. TfL and National Grid must now address grid resilience – whether through backup feeds, faster fault isolation, or investment in local substation redundancy – or face more such disruptions that upend the city’s heartbeat.

The disruption caused by the Maida Vale substation fire has been described as the worst power failure London Underground in recent years, shutting down five lines for hours.

Frequently asked questions