Gelli Felen’s original single bore tunnel opened with the first section of the Merthyr, Tredegar and Abergavenny Railway in September 1862. The line’s principal driving force was Crayshaw Bailey, a major local industrialist, whose influence was crucial in attracting investors. In 1860, it was his wife who cut the first sod to mark the start of construction but a year later, with the company’s finances looking precarious, the London & North Western Railway had to ride to the project’s rescue, taking over its management.

The Abergavenny-Brynmawr section, engineered by John Gardner, involved eight bridges, two tunnels and a climb of over 1,000 feet, placing it amongst the steepest stretches of railway in the UK with one three-mile section demanding a rising gradient of 1 in 34.

The tunnel, just 352 yards long, incorporates a curve of 90° to the north and is mostly masonry lined. Some patches of engineering brick are to be found, especially in the second southerly tunnel which appeared in 1877 when the route was doubled in an effort to maximise traffic flows. The bores are linked by two adits which are now partly flooded.

Timetabled services hit the buffers on Saturday 4th January 1958. The following day, the very last train – a special – made its way through, bringing the line’s life to an end and saving British Rail around £60,000 a year in maintenance costs.

(Alan Bowring’s photo is used under this Creative Commons licence.)

Click here for more of Sparhawk’s pictures.