Shortly after being appointed managing director (chief executive) of BSA's Automotive Division in 1956, Edward Turner was asked to design a saloon car powered by a V8 engine.

[4][5] The engine drawings were finalised by March 1958, but the saloon prototype, project number DN250, was not available for examination by the committee formed in 1958 to report on the feasibility of the V8 cars.

[8] The original version, later called the "A-spec", could reach a speed of 120 mph (193 km/h), but the chassis, a "14-gauge ladder frame with cruciform bracing" based on the Triumph TR3,[10] flexed so much that doors occasionally came open, marring its reputation.

[15][16] The SP250 had a fibreglass body, four-wheel Girling disc brakes, and a 2.5-litre hemi-head V8 engine designed by Edward Turner.

[18][19] Chrysler, whose Dodge division owned the trademark for the "Dart" model name, ordered Daimler to change the name under threat of legal action.

[23] The police cars used the Borg-Warner Model 8 three-speed automatic,[18][24][25] which the Metropolitan Police found to be better for town work and high-speed chases, and was also found to be more economical, avoiding the clutch wear that a manual car would develop with usage between 18 and 24 hours a day.

[citation needed] The "C-spec" version, introduced in April 1963, included a trickle-charger socket, a heater/demister unit, and a cigarette lighter as standard equipment.

[31] After Jaguar Cars bought the Daimler Company from BSA, William Lyons ordered a fibreglass-bodied DP250 prototype to be completed.

[33][34][35] It was shown at the 1962 Earls Court Motor Show,[35] but it was not taken up by Daimler and the body design was later used for the Reliant Scimitar.

It was also fitted with torsion bar front suspension, the same as the E-type in an attempt to improve road-holding although the car was said to be unstable.

Sir William had included many styling cues from the E-type, which was proving to be a great sales success following its launch in Geneva in 1961.

The distinctive flared wheel arches were removed from both front and rear wings, producing a much cleaner, smoother line to the bodywork.

As was customary, Sir William had the car driven round to his home, Wappenbury Hall in Warwickshire, for further consideration and asked for a viability study to be completed.

The outcome of this was that it would not be an economic proposition, as the SP250’s fibreglass body was very labour-intensive and the car took 2½ times as many man-days to build as the E-type.

In 1967, the car was spotted in storage by Peter Ashworth, an entrepreneur in the entertainments industry and a regular Jaguar customer, who wanted it for his wife.

He managed to convince the then-Jaguar MD, Lofty England, to sell him the car and it was registered LHP 307F in September 1967.

Mrs Ashworth (already an owner of a V8 saloon) apparently was not that impressed with its heavy steering, and the SP252 found its way back to the factory, where Duncan Saunders, at the time general secretary, later patron, of the Daimler Lanchester Owners Club (DLOC), took it for a test drive in early 1968.

[8] Jaguar built a prototype replacement under project number SP252 with a neater body style, but decided not to proceed with production.