LB&SCR H1 Atlantic

The LB&SCR H1 Class was a series of five outside-cylinder 4-4-2 Atlantic express locomotives designed by Douglas Earle Marsh and built by Kitson & Co of Leeds in 1905–1906, bringing the Atlantic wheel arrangement — four leading wheels, four coupled driving wheels, and two trailing wheels — to the London, Brighton and South Coast Railway's principal express services for the first time and transforming the performance of the London Victoria–Brighton main-line expresses.

Marsh based the H1 design closely on the Great Northern Railway's Ivatt Large Atlantic (C1 Class), which he had studied at Doncaster, incorporating the GNR's wide firebox layout and outside cylinder arrangement. The wide firebox, supported by the trailing pair of wheels, allowed a much larger grate area than the inside-cylinder types that had preceded it on the LBSCR, giving the H1 the sustained steaming capacity needed for the sixty-mile non-stop run at speed between London and Brighton.

The H1s entered service in 1905 and immediately demonstrated a marked improvement over the Billinton B4 4-4-0s on the Brighton expresses. They worked the LBSCR's fastest and most prestigious services — including the Southern Belle Pullman from 1908, the world's first all-Pullman electric train predecessor — through the Edwardian and early post-war period. All five passed to the Southern Railway in 1923 and continued on express duties, where they were joined by Marsh's subsequent H2 Class Atlantics. None was preserved, but the H2 Class Atlantic Beachy Head is currently being rebuilt to working order at the Bluebell Railway.