Although not laid out in the published Modernisation Plan, BR's initial approach to this huge acquisition task was to implement a pilot scheme, commissioning orders for 174 diesel locomotives from six independent manufacturers (due to currency and political considerations these were all British firms, even though several had little or no experience of diesel locomotive design and building) plus BR's own design offices and workshops. These designs were spread across the three power categories BR had decided would fulfil its mainline motive power needs. The designs commissioned deliberately represented a diverse range of engineering approaches (electric and hydraulic transmissions, four-stroke and two stroke engines, high- or medium-speed engines etc.) with numerous constructors and suppliers of engines and electrical equipment. The intention was that the most successful designs and elements proven by the pilot scheme would form the basis of the large-scale orders called for by the Modernisation Plan over the next decade.