The British Rail Class 42 Warship diesel-hydraulic locomotives were introduced in 1958. It was apparent at that time that the largest centre of expertise on diesel-hydraulic locomotives was in West Germany. The Western Region of British Railways negotiated a licence with German manufacturers to scale down the German Federal Railway's "V200" design to suit the smaller loading gauge of the British network, and to allow British manufacturers to construct the new locomotives. The resultant design bears a close resemblance, both cosmetically and in the engineering employed, to the original V200 design. Warship locomotives were divided into two batches: those built at BR's Swindon works were numbered in the series D800-D832 and D866-D870, had a maximum tractive effort of and eventually became British Rail Class 42. 33 others, D833–D865, were constructed by the North British Locomotive Company and became British Rail Class 43. They were allocated to Bristol Bath Road, Plymouth Laira, Newton Abbot and Old Oak Common. Two Class 42s are preserved, D821 and D832. Overview The Western Region of British Railways had decided upon hydraulic transmission with lightweight alloy construction for its new diesel locomotives to replace "King" and "Castle" class steam locomotives. This was partly because of the stiff gradients between Exeter and Plymouth on the Exeter to Plymouth line: to save fuel compared with hauling the additional weight of the locomotive up these gradients and allow an extra revenue-earning passenger coach to be added to the train. Mechanical details Each locomotive was powered by two Maybach 1,035 hp (D800–802) or 1,135 hp (D803–829, D831–832 and D866–870) MD650 engines coupled to Mekydro hydraulic transmissions. Although these diesel engines were of German Maybach design, they were physically manufactured by Bristol Siddeley at their factory at Ansty, near Coventry, under licence. The lower engine rating in the first three was because the first batch of transmissions could not accept more than this; a shortcoming swiftly rectified, although the technology of the time limited hydraulic transmissions to below input, hence the need for two engines. D830 Majestic was equipped with two Paxman YJXL Ventura engines rated at , each as a potential showcase of an alternative British-designed engine which might prove superior to the German Maybach. The new locomotives were substantially lighter than previous diesel-electric designs: a Class 44 Peak locomotive weighed and required 8 axles to carry it; the D800s weighed less than 80 tons and only needed 4 axles.