There will be no trains between Newbury, Reading and London this weekend as emergency engineering work is carried out.
Network Rail is testing the new electric overhead wires around the Reading area in preparation for the Electrostar trains that are due to be launched on January 2, 2018.
There will be no long-distance trains into or out of London Paddington on Saturday or Sunday due to the last minute closure.
Replacement bus services will be in place, but these will be limited and Great Western Railway is warning that all other routes in to the capital are expected to be busier than usual. Buses replace the trains between Theale and Reading this weekend.
Services from Theale and Newbury to Exeter St Davids, Plymouth and Penzance, as well as between Theale and Bedwyn will be running as usual.
If you have already bought a ticket for use on October 14 or 15 it will now be valid for travel at any time today or Monday, October 16. Or you can also get a refund on your tickets at www.gwr.com/refund
Further works taking place in the Reading area could mean additional line closures on Sunday, October 22 until 12.25pm and on Sunday, October 29 and Sunday, November 5 until 10.25am. Replacement buses will again be in operation.