The next stage of work for the electrification programme will be to test the overhead wires in the Reading area, which will have an impact on all Thames Valley and High Speed Services on Saturday 16 and Sunday 17 September.
Services between Swindon and Chippenham will be amended and connecting services to London will be impacted by this work.
Full details are available on a dedicated web page; https://www.gwr.com/travel-updates/planned-engineering/reading2017