Meet Britain's longest train - the ballast cleaner
27 January 2015 Last updated at 19:25 GMT
The "longest train in Britain" is working through the night to replace ballast on the Norwich to London line so speeds of 110mph can be reached.
Working overnight to minimise disruption to train travellers, engineers for Network Rail use a massive "ballast cleaner train" to remove the broken chippings underneath the tracks and replace them with more robust material.
Debbie Tubby reports.