The NBR 224 and 420 Classes consisted of six steam locomotives of the 4-4-0 wheel arrangement built by the North British Railway (NBR) in 1871 and 1873. No. 224 had three claims to fame: it was the first inside-cylinder 4-4-0 to run in Great Britain; the locomotive involved in the Tay Bridge disaster; and after rebuilding in 1885, was the only compound-expansion locomotive on the NBR and one of just three tandem compounds in Britain.