The LSWR O2 Class is a class of 0-4-4T steam locomotive designed for the London and South Western Railway by William Adams. Sixty were constructed during the late nineteenth century. Adams noted problem of a greatly increasing volume of commuter traffic experienced with the suburbanisation of London during the 1880’s exacerbated by few locomotive classes in the LSWR stable that could undertake commuter traffic at the desired level of efficiency. The LSWR therefore required a locomotive with attributes of power and compactness, with a small wheel size to gain acceleration on intensive timetables. Adams settled upon the 0-4-4T wheel arrangement to provide the basis of what was to become the O2 Class. The second of William Adam’s 0-4-4 designs, the O2 Class was a development of his previous T1 class of 1888. The brief was to create a locomotive able to handle mixed-traffic operations, a characteristic dictated by the smaller wheel diameter and smaller cylinders, to replace the obsolete Beattie Well Tank. A compact locomotive with high route availability was produced. Production began in 1889, with the first 20 built at the LSWR’s Nine Elms works. The success of the locomotive ensured a second batch of 30 was ordered the next year. A final batch of ten was constructed by 1895.