The Leyland National is an integrally-constructed British step-floor single-decker bus manufactured in large quantities between 1972 and 1985. It was developed as a joint project between two UK nationalised industries – the National Bus Company and British Leyland. Buses were constructed at a specially built factory at the Lillyhall Industrial Estate, Workington. Styling was carried out by the Italian vehicle stylist Giovanni Michelotti, previously commissioned by both Triumph (Herald, TR4, GT6, 2000/2500, 1300, Dolomite and Stag) and Scammell lorries (Routeman GRP cab).
It was intended to replace all the rear-engined single-decker buses offered by British Leyland, including the AEC Swift, Bristol RE, single-deck Daimler Fleetline, Daimler Roadliner and Leyland Panther.
Design
The Leyland National was built with integral, modular construction and a rear engine. All components were designed for ease of construction and replacement. Until 1978, it was always built with a roof mounted pod at the rear, housing the heating equipment, which consequently blew warm air out at roof level. At first the pod was almost the length of a bay and appeared designed to give a Trans-Atlantic feel. In 1976 a new shorter version of the roof pod was introduced along with the battery being relocated to the front under the cab. The Leyland National was available in three lengths, the majority being and . It was easy to spot the longer ones as its main side windows were all the same length, on the shorter models the windows were shorter except for one in the middle (where the exit doors were on dual door variants) which was the same length as on the longer models. The third length was , specially produced for Australian operators due to stringent axle weight limits. This used the front section of the long version and the rear section of the short version. The prototype of this latter version was sold to a Scottish operator, Rennies of Dunfermline, and was fitted out to dual purpose specification for use on express services.
The Leyland National was a simple design: all parts could be replaced. Some operators, like London Transport, bought dual door models, and then later configured some of them to single door. This was helped by the design of the body, the fact that parts were inter-changeable and that the bus was constructed using Avdelok rivets, specially designed for the National, instead of the more usual pop rivets screws or welding.
The earlier vehicles were only available in a limited number of standard colours, e.g. dark red, light red, dark green, to try to match but simplify existing operators' liveries. This just predated the decision by the National Bus Company to standardise on two colours: poppy red and leaf green. The timing was such that several vehicles were delivered in dark red paint to Ribble, who repainted them poppy red before entry into service. At London Transport's insistence, London bus red was added to the colour card, and their fleet eventually amounted to 506 examples, 69 of these being National 2s purchased for Red Arrow services, between 1973 and 1980.
In 1978, Leyland brought out a simplified model, the Series B, intended to replace the Bristol LH which had been in production since 1967 and was a type popular in NBC companies for rural routes. It was available in a single length (10.3 metres; 33 ft 9 in) and had a revised interior that had minimal lighting and without the rear roof-mounted heating unit in previous models. Heating was under the seats and was basic but effective. These vehicles were lighter, and this characteristic and the lower cost helped make extra sales. London Country bought a large number of Series Bs, which other operators quickly purchased second-hand when London Country was broken up in 1986.
The National 2 was introduced in 1979. It differed from its predecessor mainly by having a wider choice of engines, along with a new nose moulding giving it a more bulbous look and a grille to cool the new front-mounted radiator, and a revised rear end with new lights and a different engine door.
Engines
The Mark I Leyland Nationals had an 8.3-litre straight-six turbocharged Leyland 510 headless diesel engine. The Leyland 510 engine had an unusual design, in that it featured non-detachable cylinder heads; any work on the valves required the crankshaft and pistons to be removed to enable access from the cylinder bore. This engine did not prove popular with all operators, being prone to poor fuel consumption and heavy smoke production if not maintained to high standards.