First Great Western (FGW) reported delays of up to 90 minutes because of a signal failure on the line.
Between four and six trains were on the line when the signals failed, potentially delaying hundreds of pasengers.
An FGW spokesman said services had very minor delays earlier this morning, but had now returned to normal.
Train services also ran at reduced speeds into London yesterday because high temperatures had affected rail conditions. Disruption caused by the hot weather continued until about 6.30pm.
Visit www.journeycheck.com/firstgreatwestern for details.
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