Meet Britain's longest train - the ballast cleaner
The "longest train in Britain" is working through the night to replace ballast on the Norwich to London line.
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.
Network Rail said the work would help operators provide a more reliable service.
Debbie Tubby reports.