The London and North Western Railway (LNWR) Experiment Class was a class of 4-6-0 steam locomotive designed by George Whale.They were an extended version of the Whale's Precursor Class 4-4-0, with slightly smaller driving wheels. The first of the class, 66 Experiment was built in 1905 and a total of 105 were constructed up until 1910. The LNWR reused numbers and names of withdrawn locomotives, with the result that the numbering system was completely haphazard.