Don Truman saw the failings in the Marwyn which he had bought in partnership with the future Mrs Truman, Barbara Longmore (hence Bar Don), partly as a result of crashing it while testing prior to the May 1948 Prescott meeting! He developed the car himself during 1948 including a significant weight reduction, modified bodywork and smaller wheels to lower the car and improve stability. It used a JAP engine. Don attended the Shelsley meeting in June, won his heat and finished fourth in the final and fourth in the handicap at Brough in July, took sixth in the Brighton Speed Trials and eighth at Prescott in September. At the inaugural Goodwood meeting, Don managed another fourth and finished the year with a third at Weston super Mare, by far the best overall performance by a Marwyn based car.
Over the winter of 1948/49 Don made further modifications, possibly with assistance from Jack Turner. Things didn't start well with a DNF at Brough in April, after an exhaust pipe cracked, and further failures at Easter Goodwood and Silverstone for the Grand Prix. Things improved with an eighth place at Prescott in May then sixth at Shelsley on 11th June and another eighth at Prescott the following day then July Prescott brought tenth. At Blandford, Don took fifth in his heat and fifth in the final, good performances for a non-Cooper then fourth fastest time at Brighton in September. Returning to Prescott, he managed a fine fourth, then fifth overall in the 750cc class at Shelsley on 24th September but failed to finish his heat at Brough in spite of leading the first lap and could only manage fourteenth at Weston super Mare on 8th October. at the end of 1949, Don was awarded the Good Losers trophy for his efforts.
The Bardon-Turner came to be in 1950 when Jack Turner fitted alloy wheels, similar to those of Turner sports cars, better brakes and independent suspension.. Easter Goodwood proved a disappointing start to the year but things improved with a tenth in his heat for "Royal" Silverstone in May. Prescott in June brought fourth fastest time and at Brands Hatch, a podium in the non production car race and finally a win at Silverstone on 2nd July ahead of Tom Clarke's Cooper and Jack Moor's Wasp. At the Commander Yorke meeting, Don took a podium in the three lap scratch race and second, to Don Parker, in the non production car race and July Prescott brought fourth fastest time. He managed a third in the non production car race at Brands in August and second in the equivalent race in September. Don could only manage eighth at Shelsley, eleventh at Castle Combe and a DNF in the Grand Prix but improved with a fifth in the handicap heat at Brough. Don's last race of the year brought a fifth in his heat of the Open Challenge at Brands Hatch.
The final and least successful evolution of the car was for 1951 when it had new low slung body in the style of a Cooper with pannier fuel tanks and a works JAP “Sloper” engine, this new engine should have been much more suited for circuit racing than the old Speedway JAPs but it proved otherwise and the car failed to finish any race during 1951, Don later received 2 new Speedway JAP engines from the factory by way of compensation! For 1952, Don succumbed and bought a Cooper Mk VI
In 1952, Jack Turner built a new car in conjunction with Cyril Kieft using a his own design, double over head cam, four cylinder, engine however it did not produce as much power as was hoped and only two Turner Kiefts were built. Jack became well known for a series of sports and kit cars under his own name during the fifties and sixties.
The Bardon-Turner was eventually rebuilt into something like the 1950 form.