This special issue of the Civil Engineering journal is on the hugely challenging project to electrify the Great Western railway between London and south Wales in the UK.

Completed in January 2020, the GBP3 billion programme of works involved threading overhead line equipment along 650 km of live railway tracks and through dozens of historic bridges and tunnels.

The seven papers in this issue describe the many challenges and lessons learned on the first major electrification scheme in the UK for a generation.