On the weekend of 14 and 15 October, just prior to the introduction of the first IEP into service, Network Rail called a late-notice closure of the railway around Reading to carry out further testing of electrification infrastructure.

It is understood operator GWR received just 10 days’ notice from Network Rail of the plan, which closed the Great Western main line between Maidenhead and Didcot Parkway/Theale. Given this lack of notice, it was not possible for GWR to utilise diversionary routes to reach alternative London stations; during previous closures the operator has run services into both Waterloo and Marylebone. Services from Bristol and South Wales ran to Oxford, where Chiltern Railways services to London Marylebone were running; the operator said it added over 8,500 extra seats onto its Oxford to London route to provide extra capacity, with replacement buses on standby and queueing systems in place.

While it has been reported that the closure was to carry out work which was not undertaken during previous possessions, Modern Railways understands there have been several attempts to complete section proving of the newly-installed overhead wires between

Maidenhead and Reading but these have identified faults, meaning the testing had not been completed.

Diverted service: unlike the weekend of 14-15 October, scheduled engineering work in mid-September allowed diversions to be planned in advance and GWR HST services ran via Bicester Village for the first time. This is Islip on the Oxford to Bicester route on 17 September 2017, with a Paddington to Plymouth service passing.
Alan Wallwork