PlayNetwork Rail has been hit with a record £14 million fine by the Office of Rail Regulation.
It follows three serious engineering work overruns that plagued passengers over the 2007/2008 Christmas and New Year period.
The most serious of these was on the West Coast Main Line at Rugby in the West Midlands, which shut a section of the line.
The work should have been completed by the end of December 30 but overran by four days, wrecking the travel plans of thousands of workers returning to offices after the festive season.
The penalty is significantly higher than the £2.4 million handed down for failing to complete signalling work at Portsmouth in 2006.
Union leaders have expressed fears that a fine on a company like National Rail - which has no shareholders - is effectively a fine on taxpayers.
© Independent Television News Limited 2008. All rights reserved.
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