All Heathrow Express and Great Western Rail train services are due to grind to a halt from 7pm on Monday, as Aslef's strike continues.
Both operators were running restricted routes throughout the day, but are ending services early this evening.
Trains from London Waterloo towards Clapham were also being disrupted by a signalling problem on Monday afternoon, with South Western Railway said it hoped the disruption would end by 5pm.
Meanwhile no trains have run on the Chiltern Railways and CrossCountry networks all day on Monday, amid Aslef's strike over pay and conditions.
