An investigation has begun after doctors revealed that cancer treatment for a 3-year-old boy from Plymouth was carried out incorrectly.
Consultants told Elsbeth and Mike Hallam that radiotherapy beams supposed to be targeting their son's tumour, were wrongly set up.
The hospital says the problem has now been rectified and won't affect treatment.
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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.