In 1958, Austin launched the Austin-Healey Sprite, a tiny little sports car designed by Donald Healey, a model that was an instant success.

Triumph had already thought about producing a small sports car of its own and after the austere little Sprite entered the market they were convinced they could produce something that could successfully compete with it.

In January 1968 Leyland, who had been the owner of Triumph since 1961, took over British Motor Holdings, which included the Jaguar and Daimler names, together with the whole of the BMC company that included Austin, Morris and MG. The merged company was re-christened The British Leyland Motor Corporation (BLMC). One of the quirks of this merger was that the competing sports cars, the Spitfire and the MG Midget/Austin-Healey Sprite, were now being built by the same company. Nonetheless rivalry among those consumers loyal to their preferred badge was just as strong as the marketing competition had ever been.

In 1970 the Triumph arm of BLMC launched what can be called an almost complete re-skin of a car, in a style inspired by the Spitfires original Italian designer, Michelotti. Although dubbed the Mk4 it was never officially given that name by Triumph as it was feared this designation may cause confusion on account of the first Spitfire model being called the Spitfire 4.

During the re working of the car the front end was cleaned up with the loss of the trim strips on top of the bonnet sides and on the rear wings, as well as disposing of the chrome headlamp surrounds. A black plastic grille and black plastic bumper under rider covers were added to the front and the doors were fitted with more modern looking flush-fitting handles. Further body modifications included the flaring of the wheel arches and the raising of the windscreen height by 2 inches. The windscreen frame also became an integral part of the scuttle construction and so was no longer removable by simply unbolting it from the rest of the car.

The styling of the rear end was brought into line with other Triumph models of the time, such as the Stag and the 2000/2.5 PI saloon. This restyling brought about a slightly improved boot space and a rear bumper that came in one piece, instead of the previous two small bumpers on each of the rear body-corners. In fact the only outer panels to remain completely unchanged were the sills.

For this car, Triumph’s own stylists came up with a smart new hardtop with a much flatter roof panel than the previous bulbous offering. The new roof also featured opening rear quarter light windows, a flat rear screen and a frame to the soft top that was partly covered by black plastic mouldings in an effort to reduce the risk of head injury to the occupant's.

The interior of the car received a black plastic dashboard, as already introduced in the Mk3's in 1969 for the US market, instead of the more familiar Triumph trademark of a wood veneered version. Other interior modifications included the moving of the main instruments from the centre of the dashboard to a new position in front of the driver.

Later in its production life a wood-veneered dashboard was again fitted, and for the first time, black padded sun visors, safety belts and a heater that actually now came as standard on all market models. Cars that were fitted with the overdrive option now had a sliding switch on the gear knob instead of a lever on the steering column.

The Mk4 still had the 1,296cc engine from the Mk3, but to simplify the manufacturing, and the supply of parts, it was fitted with the larger con-rods of the six-cylinder engines as fitted to the GT6 and Vitesse. Contrary to popular belief the Mk4 engine was NOT detuned at this time, speculation concerning this being the result of the power output being quoted at 63bhp as opposed to the 75bhp as of the Mk3. In reality the difference in the figures only came about as a result of a change in methods of measuring power output, this now being recorded according to the German DIN system, in other words, same length - different ruler. Even so the Mk4 was slower than the Mk3, but this was due to the car being heavier, a taller final drive (3.89:1 as opposed to 4.11:1) to improve fuel economy and a new gearbox with a taller, but now synchromesh first gear.

Previous Herald and Spitfire models had some unpleasant handling properties, with the dangerous tuck-under of either one of the rear wheels whilst hard-cornering. The main reason for this was that the transverse rear leaf spring assembly of the rear axle was bolted directly to the top of the differential casing, and it wasn’t until the conception of the Mk4 that this major design weakness of the rear suspension was properly addressed. The solution the Triumph engineers came up with was both effective and cheap to implement as all that was needed was to bolt just the bottom leaf of the assembly to the differential casing leaving the others in the spring-set free to pivot around a central axis. This transformed the handling of the Mk4 and meant that finally Spitfire drivers could throw their cars about without so much danger of being launched into the scenery.

Despite all the modernisation of the car, wire wheels were still an option, but they were no longer the centre hub-lock type mounted on a splined stub-axle. As with many designs of that era the car received a much simpler and cheaper 'bolt-on' variety, which looked quite tacky. Later on the rear drive-shafts were each lengthened by one inch making a two-inch increase in the wheel-track improving the road holding properties still further.

The top speed of Euro-spec Mk4’s was 97mph and 0-60mph took about 12.5 seconds. From 1972 the Mk4 did actually get a de-tuned engine, which lowered the performance figures to a top speed of 95mph with a disappointing 14.5 seconds from 0-60mph.

Two years before the end of Mk4 production, Triumph had already introduced a 1,493cc engine to the car for the US market, but for the export model it was equipped with a single Zenith Stromberg carburettor. The extra cubic capacity had been implemented because new US emission regulations had robbed so much of the power of the old engine, forcing Triumph to increase the cubic capacity in order to keep the car competitive with market rivals. In December 1974 the 1,493cc engine was introduced in other markets and the mildly reworked model now was now called the Spitfire 1500. The engine, which was basically a longer-stroked version of the old 1300cc unit, produced 71bhp and was mated to the more simple Morris Marina gearbox. The result was that it turned the Spitfire into a genuine 100mph car for the first time in its history. Other advantages were that fuel consumption was no higher than before and the car had become much more flexible to drive, thanks to improved engine torque brought about by the longer piston stroke.

Throughout its production life many small detail changes were made to the 1500. The main visual upgrade happened in 1976, when in keeping with the fashion of the time, the bright stainless steel windscreen wipers, chromed door handles and chromed door mirrors were replaced with matte black versions. In 1977 the old steering column switchgear, still carried on from the days of the Triumph Herald, was upgraded to more modern TR7 arrangement, and a few months later again, the all-vinyl seats were replaced with cloth and vinyl covered versions.

Apart from making minor changes to the car, British Leyland did not invest in the Spitfire very well at all and although it had been planned to keep it in production until 1982, in 1980 it was realised that the 1,500cc engine could not be satisfactorily modified any further to meet with new Californian emissions regulations. Since around half of all Spitfire sales at the time took place in California this revelation meant that demand for the car dropped to the point where it had become uneconomical to produce. Also, with a basic design structure of some 18-years old, the car could no longer compete in the market place with the more modern designs like the Fiat X/19, the Triumph TR7 and Japanese models that were now being imported into the UK in large numbers.

Sadly, the last Triumph Spitfire 1500, painted in Inca Yellow, with optional hardtop and overdrive, rolled off the assembly line at Canley in August 1980. Bearing commission number TFADW5AT009898 the car was never sold and is standing to this day as an exhibit in the British Heritage Motor Museum at Gaydon in Warwickshire.