We have been treating the third rail in the south of England with anti-icing solution and trains were running around the network overnight to keep the rails clear of ice as much as possible.
Additional people were used on the ground to respond to incidents and carry out regular inspections of the infrastructure.
We will continue to work closely with train operators throughout today to deliver the best possible level of service and apologise for any disruption caused to passengers.
For the latest information, passengers should check with National Rail Enquiries or their train operator before travelling.
Services on parts of our network are being disrupted this morning as a result of adverse weather conditions which have also affected other train operators.
Cold weather conditions have caused a build-up of ice on the conductor rail which is used to power our trains.
When ice forms on the conductor rail it affects the power supply to trains and services are prevented from running normally.
As a result there are delays to services across some parts of our network. Services between Havant and Guildford are currently subject to delays of up to 60 minutes.
Trains between Waterloo and Reading are currently delayed by up to 30 minutes. Trains operating between Ascot and Guildford may be delayed by up to 40 minutes while services between Farnham and Alton are suspended.
We would like to apologise to customers for the delays to their journeys this morning.