A train has been derailed by debris on the track near Bargoed following a landslip. Network Rail say around 10 people were on board at the time but nobody was injured. Buses are replacing trains between Bargoed and Rhymney.
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The peer will attack Prime Minister Theresa May for failing to represent the 48% who voted in favour of Remain.
Paul Flynn, MP for Newport West, will open the debate in Westminster Hall.
It will represent another boost to the region, after the announcement Deca Sealand was chosen for a repair hub for defence aircraft.