Rail services along the principal corridor connecting the capital with Oxford have been thrown into disarray due to an electrical infrastructure problem.
Great Western Railway confirmed that its operations between the London terminus and the Berkshire interchange town are experiencing cancellations, delays, and incomplete journeys stemming from a failure in the overhead power system.
The incident is anticipated to persist until the evening hours, with services not expected to return to normal before 7pm on Saturday.
The operator is collaborating with the infrastructure manager to identify the source of the fault.
Travellers are being granted complimentary access to alternative transport arrangements.
Tickets valid for GWR services are being honoured on Chiltern Railways trains operating between Oxford and the London Marylebone terminus, South Western Railway services running between Reading and London Waterloo, and sections of the London Underground network served by the Bakerloo and Jubilee lines.
Road-based replacement vehicles have not yet been arranged, though the situation remains under active review.
Passengers whose booked services are cancelled may instead travel on any available option up to two departures before or after their original scheduled train.
Holders of peak-time or restricted tickets may still use their existing travel documents without additional payment.
Station personnel, journey planning tools, and real-time departure information screens are all available to assist customers in identifying suitable alternative routes.
The rail company stated that no passenger would be left unable to complete their journey.
Telephone assistance is available via the designated helpline number.
Those experiencing delays of a quarter of an hour or more qualify for Delay Repay compensation and have been advised to retain their tickets before submitting a claim through the official website.
The operator has expressed regret for the disruption while engineering teams continue their efforts to restore full service.