Passengers trying to get to Cardiff are now heading from Didcot back to Reading. Those going to Swindon and Bristol are awaiting a fleet of buses to help them reach their destination. Trains from Reading to Wales will go a long route.
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Southampton's marathon runners worked up a sweat as temperatures touched 20c but there was help on hand to keep them cool.
The Duchess of Cambridge has been driven to St Mary's Hospital in London in the "early stages of labour", Kensington Palace has said.
The Duchess of Cambridge has been on maternity leave since the week before Easter.