The locomotives were introduced during July 1910 by Charles Bowen-Cooke following the succession of George V, construction continued until 1915. They were essentially superheated versions of the LNWR Whale Precursor Class. At the same time, similar non-superheated Queen Mary Class engines were also built but all of these acquired superheaters as the advantages of superheating became clear and were absorbed into the George the Fifth Class.
A total of 90 Georges were built, and all were named. The LNWR reused names and numbers from withdrawn locomotives, with the result that the numbering system was completely haphazard.
All of the Georges passed into London, Midland and Scottish Railway (LMS) ownership on the grouping in 1923. The LMS gave them the power classification 3P. The LMS renumbered them into a more logical series of 5320–5409, and later in 1936/37 those had not been then withdrawn were again renumbered by the addition of 20000 into the 25320–25409 series to make room for Black Fives. It was also at this time that a few of the names were removed so that they could be applied to new LMS Jubilee Class engines.
Withdrawals started in 1935, and by 1939 only nine remained. British Railways (BR) inherited three in 1948: 25321, which was withdrawn in February that year, and 25350 and 25373, which were allocated the BR numbers 58011/2 in March but never carried them as both were withdrawn in May that year. None have been preserved.
On 14 August 1915, locomotive No. 1489 Wolfhound was hauling a passenger train when it suffered a mechanical failure in its motion, with the result that the opposite track was damaged. A mail train was derailed on the damaged track at Weedon, Northamptonshire. Ten people were killed and 21 were injured.
† Locomotives that had 20000 added to their number from 1934
‡ Locomotives that had 20000 added to their number from 1934, and were allocated the BR numbers 58011 (25350) and 58012 (25373 Ptarmigan). Neither survived long enough to carry them.
Baxter, Bertram (1979). Baxter, David (ed.). British Locomotive Catalogue 1825–1923, Volume 2B: London and North Western Railway and its constituent companies. Ashbourne, Derbyshire: Moorland Publishing Company. pp. 272–275. ISBN0-903485-84-2.
Casserley, H. C. & Johnston, Stuart W. (1974) [1966]. Locomotives at the Grouping 3: London, Midland and Scottish Railway. Shepperton, Surrey: Ian Allan. pp. 64–65. ISBN0-7110-0554-0.
Goodman, John (2002). L&NWR Locomotive Names / A Sequel to LMS Locomotive Names. Locomotives of the LMS. Peterborough: RCTS. ISBN0-901115-90-8.
Yeadon, W. B.Yeadon's Compendium of LNWR Locomotives, Vol 1: Passenger Tender Engines.