The middle of the 19th century saw the slow encroachment of the railway through Wensleydale. Reaching Leeming Bar in 1848, Leyburn in 1855 and Askrigg in 1877, a through route was finally secured on 1st October 1878 when the North Eastern and Midland railways met end-on in Hawes.
The Midland's branch - running 5 miles 1,577 yards - was more demanding in engineering terms as it traversed the rugged landscape at the head of the dale. The cost per mile was £40,000.
Making a disproportionate contribution to this figure was Mossdale Head Tunnel, a short single-track bore of 245 yards. Both portals are masonry, with wing walls and buttresses either side of the entrance. Considerable work was carried out to improve drainage in their approach cuttings. Trains entering from the west did so on a southerly curve - the tunnel then straightening. Platelayers were catered for with refuges in both walls.
The last passenger train passed through on 16th March 1959. Since then the tunnel has paid the price for surrounding ground movement and the absence of a maintenance regime. For around 30 yards east of its midpoint, the crown of the arch has been forced upwards, resulting in serious distortion in the lining. Lesser failings are also apparent in other areas.
Now used as a store for farm machinery, the tunnel features in the long-term aspirations of the Wensleydale Railway to reconnect its railhead at Redmire with the Settle & Carlisle at Garsdale Head. Before then, significant and costly remedial work would have to be completed or the structure opened out.