Britain's first modern high speed line may have been the Selby Diversion. Its first 300km/h line may have been High Speed 1. But the first inter-city railway that embodied the design elements we see of high speed lines today was - arguably - the Great Western Railway. 130 years after its opening it also became Britain's first 200km/h railway.

It may have been over-engineered by Brunel, but this was very much in the favour of the engineers of the 1970s when they upgraded much of the GWR for 125mph running... This week's #RailNatter looks at what these upgrades involved - and we'll think on what we can learn from these works today.

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