BR decided that it would be desirable to have a single-cab Type 1 locomotive that provided good visibility in both directions. The organisation thus approached various locomotive manufacturers with its request for proposals to meet this requirement. Among the companies that chose to respond was the British manufacturing interest Clayton Equipment Company, which had already acquired considerable experience in the design and production of various mechanical elements of existing Type 1 locomotives, and was keen to pursue its own design. Following a review of submissions BR opted to select Clayton's submission, ordering 117 locomotives off the drawing board, and announced to the railway press that these locos were to be the new Type 1 standard. Production of locomotives D8500–D8587 was performed in-house by Clayton between September 1962 and February 1965, with subcontractor Beyer, Peacock and Company of Manchester delivering D8588–D8616 between March 1964 and April 1965. Design The Class 17 locomotive incorporated several features that were relatively novel amongst its contemporaries; to achieve the desired visibility from a single cab, it was decided to place it in a central position and use relatively low engine bays. This arrangement contributed heavily to a key design decision: despite the widespread availability of engines capable of generating sufficient power on their own, the propulsion arrangement opted for was a pair of relatively small six-cylinder horizontal engines, each being placed on either side of the cab. According to the manufacturer, the increased maintenance costs of two engines over a single unit was a worthwhile trade-off for the improved visibility made possible by such an arrangement. The majority of the Class 17s were powered by a pair of Paxman 6ZHXL engines of each – a power unit originally intended for diesel railcars, but not adopted. The last two of the Clayton-built batch, D8586/87, had a pair of Rolls-Royce Type D engines. These suffered several crankcase failures, leading to two of the four being replaced by Paxman units. The propulsion arrangement also featured an electric transmission, rather than a hydraulic counterpart; this was a somewhat unusual design choice for the era as the vast majority of contemporary twin-engined locomotives had opted for hydraulic transmissions. Fuel was supplied from a single tank mounted in a central position. An auto-cutoff system was integrated to prevent overfilling of the tank; several other warning systems, such as for the radiator header tank fluid level, were also present. A total of