The Manchester & Milford Railway set out with the ambitious intention of linking the industrial centres of the north-west and Midlands with Milford Haven Docks. From a junction on the Mid Wales Railway at Llanidloes, it would head south-west to join the Carmarthen & Cardigan Railway at Pencader Junction, a route of around 47 miles.

Despite some local opposition, the proposal received parliamentary approval in 1861. First to be constructed was the relatively easy southern section – 27 miles of single track from Pencader to Strata Florida. This opened in 1866. Work also started at the northern end from Llanidloes to Llangurig. But, with money running out, ahead of them was 15 miles of daunting engineering to drive the line through the mountains, including a 1.25-mile long tunnel between the Wye and Myherin valleys. Instead a 14-mile deviation was created, taking the route in a north-westerly direction to reach Aberystwyth. The connection was made in 1867.

At Tynygraig the line passed through a spur of land via a tunnel of 86 yards, located just south of where Caradog Falls Halt would open in 1932. Structure number AYT2/29m21ch, it is built entirely in blue brick except for the two keystones. The arch is supported on vertical sidewalls incorporating a refuge which frames an anticlinal fold of sandstone layers at its rear. The south portal is a small affair at the end of a steep-faced rock cutting; the northern portal is rather more substantial.

The section of line through the tunnel (Aberystwyth-Strata Florida) succumbed to flooding on 12th December 1964. Passenger services continued by road until the scheduled closure date of 22nd February 1965, after which the line south of Strata Florida also shut.

Today parts of the trackbed have been incorporated into the Ystwyth Trail cycle route although this bypasses the tunnel as the land either side of it is in private ownership. The structure itself, which supports a highway, is looked after by British Railways Board (Residuary).

Paul Castle, who lived in Tynygraig from 1960-66, has written to tell us that “I fear that, with two of my cousins, I may well have been responsible for the flooding [that closed the line]! Myself, aged four, and my cousins, aged five and six, always played by the [railway] halt as we were not allowed on the road above the cottage or near the [Caradog] Falls either.

I can remember building dams along the water runs beside the track and my mother calling us and giving the customary clip around the ear for playing in the water. Then we went indoors. I also recall not being allowed out for a day or so because of heavy rain. The following day we saw a train and crew at the halt and went to look, only to find 50 metres of track high and dry from the ballast. On behalf of myself and my cousins, I’m sorry!”