The most numerous 4-wheel Flatrol on BR reported by Essery & Morgan as derived from LMS diag. 96A, but they are different! BR built 33 for revenue use on diag 2/512 and a further 15 for engineers use on diag 2/904 which had roller bearings. 29ft. oh, 24ft wb.note some floors strengthened and baulks removed. All in collection are in engineers use, it includes details.