LNER A3 Class

The 1925 LNER/GWR Locomotive Exchanges had been a wake-up call for the LNER's motive-power policy. Collett's GWR Castle Class, running on LNER metals against the A1s, had outperformed the LNER's 1922 Pacifics in dynamometer-car tests, demonstrating that the A1's 180 psi boiler pressure was a serious limitation. Sir Nigel Gresley's response was the A3, an A1 redeveloped with higher boiler pressure, long-travel valves, and other detail improvements designed to address the 1925 Exchange findings.

The first new-build A3, No. 2743 Felstead, was completed at Doncaster Works in November 1928. The class's key improvements over the A1 were: boiler pressure raised from 180 psi to 220 psi (with cylinder bore reduced from 20 in to 19 in to balance the higher pressure); long-travel piston valves (8-inch travel against the A1's 6-inch), giving substantially improved steam distribution; and detail improvements to the steam circuit, valve gear, and ash-pan arrangements.

From 1928 onwards Gresley began progressive rebuilding of the existing A1 Pacifics to A3 standard. The conversion was protracted, engines were rebuilt as their original boilers came due for renewal, and continued through to 1948. By that date all 52 original A1s had been rebuilt to A3 form (with the exception of No. 4470 Great Northern, which had been rebuilt by Thompson in 1945 to a unique A1/1 configuration).

New-build A3s continued through to 1935, by which date 27 new-build A3s had been added to the fleet, bringing total A3 numbers to 79 (27 new-build + 51 A1 rebuilds + 1 retained as A1/1). The introduction of the streamlined A4 Class from 1935 onwards reduced the demand for new A3s, but the existing class remained in front-line service for another twenty years. From 1959 many A3s received the Kylchap double blastpipe and chimney (developed for Mallard), which substantially improved steaming.

The A3s were the East Coast main line's mainstay express engine for nearly forty years. The principal services they worked included the Flying Scotsman (the celebrated non-stop summer-only working from London King's Cross to Edinburgh, introduced 1928, the first regular non-stop steam-hauled service in the world for the 392-mile route, made possible by corridor tenders for crew changeover); the Capitals Limited (the all-year-round King's Cross–Edinburgh service); the West Riding Limited; the Aberdonian; and the Talisman.

The most famous service moment came on 30 November 1934 when No. 4472 Flying Scotsman, hauling a special London–Newcastle test train, was officially recorded at 100 mph between Leeds and York, the first British steam locomotive to be officially recorded at this speed. The achievement was widely celebrated and became one of the most iconic moments of British railway history.

The introduction of the streamlined A4 Class from 1935 displaced the A3s from the very fastest services (the Silver Jubilee, the Coronation), but the class remained on the principal LNER East Coast services through the wartime years and into BR ownership. The Kylchap double blastpipe modification of 1959 onwards gave the class another five years of useful service life, without it, the A3s would likely have been withdrawn alongside the A1/1 in 1962.

The introduction of the Class 55 "Deltic" diesels from late 1961 progressively displaced the A3s from the principal East Coast main-line services. Withdrawal accelerated through the early 1960s. The last A3 in BR service was No. 60052 Prince Palatine, withdrawn from York shed in January 1966. Of the 79 A3s, only one was preserved: No. 60103 Flying Scotsman.

The classic Gresley Pacific outline, a three-cylinder 4-6-2 with parallel boiler, wide Belpaire firebox supported by trailing axle, and high-pitched cab. The A3 is distinguishable from the A1 only by the slightly different chimney profile (the A3 having taller and narrower chimney from new) and later by the Kylchap double blastpipe and chimney fitted from 1959 onwards. The A3 is distinguishable from the A4 by the absence of streamlined casing, the A3 retained the conventional Pacific outline throughout. The class wore LNER apple green (most of LNER period), then BR Brunswick green from 1949. The preserved 60103 Flying Scotsman has been turned out in successive preservation periods in LNER apple green, BR Brunswick green and other historical schemes.

2743 Felstead (later 60087), first new-build A3, completed at Doncaster in November 1928. The engine that demonstrated the new design's 220 psi performance and confirmed Gresley's decision to rebuild the entire A1 fleet to A3 standard. Withdrawn 1962.

4472 / 60103 Flying Scotsman, the most famous British steam locomotive. Originally built as A1 No. 1472 in February 1923; rebuilt to A3 standard in January 1947. On 30 November 1934 became the first British steam locomotive to be officially recorded at 100 mph (between Leeds and York, the southbound on a special London-Newcastle run). Sold to Alan Pegler in 1963 on withdrawal from BR; toured the US (1969–1970) and Australia (1988–1989); restored at the National Railway Museum 2006–2016 and currently main-line registered. Currently turned out in BR Brunswick green livery.

60052 Prince Palatine, last A3 in BR service, withdrawn from York shed in January 1966.

60103 / 4472 / 502 / 1472, Flying Scotsman has carried successively GNR No. 1472 (1923), LNER No. 4472 (1924 onwards), 502 (1946 LNER renumbering), and 60103 (BR from 1948). The engine is the only surviving example of the entire A1/A3 family.

LNER era (1928–1947): the class was concentrated on the principal East Coast main-line services. Major A3 allocations were at King's Cross Top Shed (the largest contingent), Doncaster (works-related), York, Newcastle Heaton, and Edinburgh Haymarket. The class worked the Flying Scotsman, the Capitals Limited, the West Riding Limited, the Aberdonian, and the principal Anglo-Scottish expresses. Selected examples carried the corridor tender for the Flying Scotsman non-stop service from London to Edinburgh, a 392-mile non-stop run requiring crew changeover en route, the world's longest regular non-stop scheduled steam working.

British Railways Eastern Region (1948–1966): continued at largely the same depots through the 1950s. The introduction of the streamlined A4 Class from 1935 had displaced the A3s from the very fastest services, and from the early 1960s the Class 55 "Deltic" diesels began to displace them from the principal East Coast main-line work. The Kylchap double blastpipe modification of 1959 onwards extended the class's effective service life by five years. The last A3 in BR service was No. 60052 Prince Palatine, withdrawn from York shed in January 1966.

LNER apple green (1928–1939): the standard LNER apple green with elaborate yellow-and-black lining, polished brass safety-valve casing, and the LNER coat of arms or "L.N.E.R." lettering on the tender. Most A3s wore apple green throughout the LNER period.

LNER unlined black (1942–1949): wartime austerity saw most A3s appear in unlined plain black with shaded "L.N.E.R." lettering. Apple green progressively returned post-war.

British Railways apple green (1948–1949): some examples briefly carried experimental BR apple green with the early lion-and-wheel emblem.

British Railways Brunswick green (1949–1966): from 1949 BR-standard lined Brunswick green became the dominant final livery, with the early lion-and-wheel emblem and (from 1956) the late BR crest. Most A3s spent the bulk of their BR years in Brunswick green.

Preservation (Flying Scotsman, 1963–present): the surviving 60103 has been turned out in numerous successive liveries, LNER apple green (most preservation periods), BR Brunswick green (1990s), BR experimental wartime LNER livery, and various permutations for charter and special-event purposes.