On Easter Monday 1896 the ribbon was cut on the Snowdon Mountain Railway's inaugural ride – but all did not run smoothly.

On the way back down the mountain (at 3,560ft the highest in England and Wales) the steam locomotive LADAS derailed and plunged off the edge of a cliff. The driver and fireman leapt to safety.

Even though the carriage being pulled behind ground safely to a halt, two passengers also jumped out. One, Ellis Griffith Roberts, sustained fatal injuries in the fall.

The railway – which runs five miles up the side of the mountain from the village of Llanberis to within 60ft of the summit – was mothballed while a safety review ensued.

Eventually it was decided to refit the rack-and-pinion track (based on a design pioneered in the Swiss Alps) with an additional safety feature: a steel girder running the length of the track to lock trains in.

The new design was completed in 1897 and has remained in place ever since – the only one of its kind in the world.

This winter, though, the railway has embarked on a 10-year £2.6m project to rip up the old Victorian track and replace it with a modern design which does not rely on the safety girder.