This little bridge near the heart of Darlington has a wondrous and under-appreciated history. The Skerne Bridge is officially the world’s oldest railway bridge in continuous operation. The bridge was constructed as part of the Darlington to Stockton railway in 1825, the world’s first public railway to use steam trains. The line connected collieries in Shildon with Stockton-on-Tees, via Darlington, the home town of the family that funded the world’s first railways. In that same year, George Stephenson’s Locomotion No. 1, the world’s first steam locomotive, crossed the bridge. The…