The A12 locomotives of the London and South Western Railway were built between the years 1887 and 1895 to the design of William Adams. Ninety of the locomotives were built; numbered 527-556 (built at Nine Elms Works); 607-646 (Neilson and Company (although officially known as O4 class); 597-606 and 647-656 (Nine Elms), they were unusual for their time. The wheelbase type (0-4-2) was being built by few of the other railway companies, and were soon being phased out (the Great Northern Railway had 150 such locomotives). They bore the nickname "Jubilees", because the first batch appeared in the Golden Jubilee of Queen Victoria's reign.
All 90 passed to the Southern Railway in 1923. Withdrawals started in 1928, with four of the class surviving to Nationalisation, but all were withdrawn in the first year of British Railways. None of the locomotives were preserved.