Wylam Dilly is the second oldest surviving railway locomotive in the world;[1][2][3] it was built circa 1815 by William Hedley and Timothy Hackworth for Christopher Blackett, the owner of Wylam colliery, west of Newcastle upon Tyne.

[5] Because it proved too heavy for the cast iron plateway in its original form, the locomotive was rebuilt with eight wheels in 1815, but returned to its original design in 1830 after the track was relaid with wrought iron rails.

The first steam locomotive of its class,[2] Puffing Billy, is in the Science Museum in London.

[8] In 1822, the locomotive was temporarily mounted on a keel and served as the engine for a steam paddlewheeler that ferried strikebreakers on the River Tyne.

The research results, released in late 2008, showed that Wylam Dilly was built after Puffing Billy, incorporating improvements on the locomotive's design that were not present in Puffing Billy.