British Railways, as part of its dieselisation scheme, contracted Clayton Equipment Ltd to supply eighty-eight diesel-electric locomotives (what would later be known as the Class 17), and other orders were fulfilled for international customers from nations as diverse as Australia, Korea, Cuba and Poland.

[4] A £5 million contract by British Railways for 88 mainline diesel electric locomotives followed during the same year, supplemented by 1.75 million order for ten 2,500 hp (1,900 kW) models that were exported to Cuba was obtained whilst, at the time, the company sales, particularly of mining and tunnelling locomotives, which were primarily for the export market, also continued to rise.

Clayton Equipment supplied a number of these machines which were put into service, before being asked to develop a locomotive that could negotiate steeper gradients.

Clayton Equipment designed and manufactured a special rubber-tyred locomotive of especially small size to work in mines, and this became one of its most popular products.

After a number of changes of ownership at higher levels, during which time Clayton Equipment Ltd established itself as a market leader in underground rail haulage solutions.

International Combustion was acquired by Clarke Chapman Ltd of Gateshead in 1974 and in 1979 the organisation merged with Reyrolle Parsons of Newcastle, manufacturer of large steam turbines for power stations, etc., to form a new company called Northern Engineering Industries which at one stage employed in the region of 35,000 people.

Recent advances include the world's first EU Stage IV diesel locomotives for use on 100 km Crossrail project, used to run trains for the installation of track, cable management systems, cross passage doors, ventilation, walkways, drainage, fire mains and lighting (Elizabeth Line in London).

Operating from both the on-board traction battery and the 3rd/4th rail supply retaining the existing chassis, cab, brakes and axles to reduce compliance issues.

The supply of two Clayton battery-diesel 80 tonne locomotives will enable Sellafield Ltd to realise significant commercial benefits from reduced operation and maintenance costs.

An agreed contract with Beacon Rail Leasing for the supply of 15 innovative Clayton battery-diesel 90 tonne locomotives along with options for a period of three years.