Network Rail chief executive Sir David Higgins said: "The Grayrigg derailment in 2007 resulting in the tragic death of Mrs Masson was a terrible event. Within hours it was clear that the infrastructure was at fault and we accepted responsibility, so it is right that we have been fined.
"Nothing we can say or do will lessen the pain felt by Mrs Masson's family but we will make the railways safer and strive to prevent such an accident ever happening again.
"We have learnt from the accident, determined to recognise what we got wrong and put it right. An event like this affects everyone in the company, and especially those with responsibility for the track."
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