There are delays on South West Trains between Salisbury and Exeter St Davids after an earlier signalling problem.
Disruption is expected until 6.30pm.
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Bridgwater and West Somerset is considered a Conservative safe seat - in 2010 they had a majority of over 9,000 votes.
Camborne and Redruth is a marginal seat. The Conservatives won it in 2010 by just 66 votes - a 0.16% majority.
The Liberal Democrats have held North Cornwall since they won it from the Conservatives in 1992. The seat is a Conservative target in 2015.