The LSWR T3 class was a class of express passenger 4-4-0 steam locomotives designed for the LSWR by William Adams. Twenty were constructed between 1892–1893.  The class were numbered 557–576 and had been intended as a variant of the X2 class with slightly smaller driving wheels. In reality, the coupled wheelbase was lengthened by 6 inches and the locomotive was fitted with a deep firebox 6 feet 10 inches long – the largest firebox of any of Adams' designs - with a 19¾ square foot grate area.

All passed to the Southern Railway at the grouping in 1923. Withdrawals started in 1930, and by the end of 1933 only three remained. No. 557 went in 1936, 571 in 1943, and the last, 563 was retired in August 1945 and set aside for preservation, at which point it had run 1.5 million miles. From May to October 2011, it was in Toronto, Ontario, on loan for use in a theatrical production of The Railway Children at Roundhouse Park, a role it reprised from December 2014 to January 2017 when the production was staged at King's Cross, London.