Stars into Castles in 1923, and then producing the largest of them all, the four-cylinder King class, in 1927. He also produced slightly smaller types for mixed traffic (either passenger and goods) duties, the Hall class in 1928, the Grange class in 1934, and the Manor class in 1934. All these continued to carry appropriate names. For lighter goods services he produced his own standard 0-6-0, the 2251 class. It was under Collett's control that diesel power first appeared on the GWR. He introduced the first streamlined rail cars in 1934 and by 1942 38 had been built, although the latter ones had more angular styling. Some were configured for long distance express services with buffet counters, others for branch line or parcels work, and some were designed as two-car sets. Sentinel geared locomotive (0-4-0 TG): 12 1101 Class (0-4-0 T): 1101–1106 1366 Class (0-6-0 PT): 1366–1371 1400 Class (0-4-2 T): 1400–1474 (renumbered 1946 from corresponding numbers in 48xx group – below) 2251 Class (0-6-0): 2200–2299, 3200–3219 2884 Class (2-8-0): 2884–2899, 3800–3866 3100 Class (2-6-2 T): 3100–3104 Earl or Dukedog Class (4-4-0): 3200–3228, 3265 (later 9000–9028, 9065) Castle Class (4-6-0): 4073–4099, 5000–5099, 7000–7037 4575 Class (2-6-2 T): 4575–4599, 5500–5574 4800 Class (0-4-2 T): 4800–4874 (later 1400–1474) Hall Class (4-6-0): 4900–4999, 5900–5999, 6900–6958 5101 Class (2-6-2 T): 5101–5199, 4100–4179 5205 Class (2-8-0 T): 5205–5264 5400 Class (0-6-0 PT): 5400–5424 5600 Class (0-6-2 T): 5600–5699, 6600–6699 5700 Class (0-6-0 PT): 57xx, 67xx, 77xx, 87xx, 97xx, 36xx, 37xx, 46xx, 96xx 5800 Class (0-4-2 T): 5800–5819 King Class (4-6-0): 6000–6029 6100 Class (2-6-2 T): 6100–6169 6400 Class (0-6-0 PT): 6400–6439 Grange Class (4-6-0):6800–6879 7200 Class (2-8-2 T): 7200–7253 7400 Class (0-6-0 PT): 7400–7449 Manor Class (4-6-0): 7800–7829 8100 Class (2-6-2 T): 8100–8109 GWR diesel shunters: Diesel shunters 1 and 2 GWR railcars: Diesel railcars 1–38 Frederick Hawksworth (1941-1949) Frederick Hawksworth only became the Chief Mechanical Engineer in 1941 and the Second World War meant that his new designs were few. He updated Collett's Hall class to produce the GWR 6959 Class, known as "Modified Halls", and produced the last GWR 2-cylinder 4-6-0s, the County class 4-6-0, which ended a tradition that had begun with the Saint class 42 years before. Their boilers were based on those of the LMS Stanier Class 8F 2-8-0, a number of which had been built at Swindon during the War. Other designs included three designs of 0-6-0PT: the taper