SR Merchant Navy

By 1937 the Southern Railway needed a heavier express engine for the West of England line. Oliver Bulleid had been recruited from the LNER in 1937 (as Sir Nigel Gresley's former Personal Assistant) and was determined to produce a radical, technically-advanced design. Bulleid's brief was a Pacific to handle the heaviest Southern boat trains and West of England expresses; his approach was to incorporate as many engineering innovations as possible in a single design.

The Merchant Navy was the result. Bulleid's key innovations were: a welded all-steel boiler (among the first British examples at express scale); thermic siphons in the firebox (copied from the contemporary Pennsylvania Railroad K4s); 280 psi pressure (the highest of any British express); chain-driven valve gear in an enclosed oil bath (Bulleid's patent design intended to give continuous low-friction operation); and an "air-smoothed" rectangular casing (intended to keep the engines clean and reduce labour in shed). The cylinders were notably small for a Pacific (18 × 24 in, against the Princess Coronation's 16½ × 28 in) but the high pressure compensated.

The first engine, 21C1 "Channel Packet", was completed at Eastleigh Works in February 1941, wartime conditions slowing production. The class's wartime priority was express freight, but the engines were progressively cascaded onto the heaviest expresses as conditions allowed. The first ten engines (21C1–21C10) were completed by 1944, with the second batch (21C11–21C20) following 1945–1948 and the post-Grouping batch (21C21–21C30) 1948–1949.

The Bulleid features proved problematic in service. The chain valve gear stretched and required regular tensioning; the oil bath leaked; the welded firebox developed cracks. The class's availability was substantially below expectations, and from 1953 BR Southern Region engineering chief Ron Jarvis (under CME R. A. Riddles) developed a comprehensive rebuild scheme. Between 1956 and 1959 all 30 Merchant Navies were rebuilt at Eastleigh, chain gear replaced with three independent Walschaerts gears, casing removed (revealing the boiler), pressure reduced to 250 psi, and various other detail changes. The rebuilt engines were dramatically more reliable, with availability rising from approximately 60% to over 80%.

The Merchant Navies were the Southern Region's top-link Pacifics from 1941 onwards. They worked the Atlantic Coast Express (London Waterloo to Plymouth and Padstow), the Bournemouth Belle, the Royal Wessex, and the principal boat trains from Victoria. The 1948 BR formation gave the Southern Region 30 engines (the first 20 plus the post-Grouping batch), sufficient for all top-link duties.

The original Bulleid engines' availability problems progressively concentrated minds. By 1953 the case for rebuilding had become overwhelming, and the Jarvis-led rebuild programme of 1956–1959 transformed the class. Rebuilt engines worked the principal Southern Region expresses through the 1960s, the Bournemouth Belle and Atlantic Coast Express continuing into BR steam's closing years. The Bournemouth electrification of July 1967 ended Merchant Navy main-line steam working; the very last Merchant Navy in BR service, 35028 Clan Line (privately preserved by the Merchant Navy Locomotive Preservation Society), was withdrawn from Nine Elms in July 1967.

The Merchant Navy was thus among the very last BR steam Pacific classes in service, and its late retirement and high-profile preservation profile have given the class continuing main-line presence through the heritage era. Several Merchant Navies have been main-line registered for charter haulage, with 35028 Clan Line giving the longest preservation operating record.

Two distinct outline phases. Original Bulleid (1941–1959): the celebrated air-smoothed "spam can" outline with a wedge-shaped front and rectangular slab-sided casing covering boiler, smokebox, and cylinders. The casing was deliberately not described as "streamlined", Bulleid termed it "air-smoothed" because its purpose was operational (cleaner engines requiring less labour for cleaning) rather than aerodynamic. Front-end air vents distinguished the original design. Rebuilt (1956 onwards): conventional British Pacific outline with three independent Walschaerts gears, smoke deflectors, and a removed casing. The rebuilt locomotives retained the welded steel boiler at reduced pressure (250 psi) but lost most of the original Bulleid features. The class is named after British and Allied shipping lines and named ships, a wartime tribute to the merchant fleet that supplied Britain through the Battle of the Atlantic.

21C1 Channel Packet (later 35001), the class prototype, completed at Eastleigh Works in February 1941. The first British Pacific to enter service since the LMS Princess Coronations of 1937. Rebuilt 1959. Withdrawn from BR November 1964 and broken up.

21C5 Canadian Pacific (later 35005), built April 1941. Rebuilt 1959. Withdrawn 1965 and privately preserved. Currently main-line registered with the Mid-Hants Railway.

35028 Clan Line, completed at Eastleigh in December 1948, one of the first BR-built Pacifics. Rebuilt 1959. Withdrawn from BR July 1967, among the very last Merchant Navies in BR service. Privately preserved and currently main-line registered with the Merchant Navy Locomotive Preservation Society. The most extensively preserved-operated Merchant Navy.

35029 Ellerman Lines, built at Eastleigh January 1949. Withdrawn from BR September 1966 and preserved by the National Collection. Currently exhibited at the National Railway Museum, York, sectioned (cut longitudinally) to show internal construction, the most-photographed Merchant Navy and a teaching exhibit.

Other preserved Merchant Navies include 35005 Canadian Pacific, 35006 Peninsular & Oriental S.N. Co., 35009 Shaw Savill, 35010 Blue Star, 35011 General Steam Navigation, 35018 British India Line, 35022 Holland America Line, 35025 Brocklebank Line, 35027 Port Line, and 35029 Ellerman Lines, eleven engines spread across the heritage railway network in various states from working order to long-term restoration.

Southern Railway era (1941–1947): the class was allocated to the principal Southern Region top-link sheds, Nine Elms (London Waterloo), Salisbury, Exmouth Junction, Stewarts Lane (London Victoria), Bournemouth, and Brighton. Each shed worked the principal expresses on its lines: Nine Elms and Salisbury sharing the Atlantic Coast Express, Stewarts Lane the Continental boat trains, Bournemouth the Bournemouth Belle.

British Railways Southern Region (1948–1967): the same allocations continued through the BR era. The first ten of the post-1948 batch (35021–35030) joined the existing twenty.

Rebuilds (1956–1959): rebuilds were progressively distributed across the Southern Region top-link sheds. By 1962 all 30 engines had been rebuilt and the class was working the principal expresses in conventional form.

Final years (1965–1967): the Southern Region was the last BR region to electrify its principal main lines. The Merchant Navies survived through the mid-1960s on the Bournemouth and West of England services, with last withdrawals from Nine Elms and Weymouth in July 1967, among the very last steam Pacifics in BR service.

Southern Railway malachite green (1941–1947): the original engines were outshopped in SR malachite green with horizontal yellow stripes, a distinctive and visually striking livery for the air-smoothed casing.

British Railways experimental blue (1948–1949): some early-BR examples briefly carried BR experimental dark blue lined out in black and white.

British Railways Brunswick green (1949–1967): from 1949 the class wore BR-standard lined Brunswick green with the early lion-and-wheel emblem (later the late BR crest from 1956). This was the dominant livery on both original Bulleid and rebuilt engines through to the end. A small number briefly carried experimental BR malachite green in the late 1940s.

Preservation: preserved Merchant Navies have appeared in SR malachite green (notably 35005 Canadian Pacific in operating condition), BR Brunswick green with both BR emblems, and (rarely) experimental BR malachite green. 35029 Ellerman Lines is preserved in BR Brunswick green, sectioned.