Triumph TR3 Beta

By Marsden's account to the TR Drivers Club, the cars were built by Ray Bates's team after it had moved from the Radford works to Fletchamstead North, part of the Canley headquarters, and Marsden himself widened the TR3's track; Gordon Birtwistle, the high-speed development engineer, told the club that he had done a lot of testing at the Motor Industry Research Association's track in the black car. Revington TR lists the parts meant for the TR4 that went into the prototypes: the all-synchromesh gearbox (transmission), a wider rear axle, rack-and-pinion steering "with stalk type head controls", and the wider-track chassis. A Moss Motoring profile of 2015 adds the larger engine, and says that the twin-cam engine of the Le Mans cars was considered too.

The chassis is the part that puzzles its owner. Revington TR finds that its strut box in the engine bay is unlike any other and that it has extra lugs for brake hoses, which suggest experiments with the brakes; a former development engineer told Neil Revington that he had been "tasked with widening a TR3A chassis".

Wikipedia, citing David Knowles, says that Ray Henderson cut a chassis numbered X693 in half lengthwise and widened it, and that Standard-Triumph's board minutes of 19 September 1960 mention the project; no source read confirms either. When the cars were built is itself not settled: Revington TR says "the early 60's", and the date of 1960 rests on Wikipedia's minutes and on later accounts.⁠source 1​source 2​source 3​source 4

Revington TR, which owns the black car, says the Beta was a cheaper way to update the TR3: Triumph's engineers came up with it, its page says, "when Triumph couldn't afford the tooling for the new TR4 body shell penned by Giovanni Michelotti", and when they already had a number of TR4 chassis to hand. A Moss Motoring profile tells it the same way, and Revington TR adds that the idea was dropped when Leyland paid for the TR4's tooling.

The TR Drivers Club, drawing on Marsden, puts it the other way round: the Beta came first, built, the club suspects, to improve the handling, and the TR4 then took its chassis, suspension and running gear. It sets out to correct the third account, which it calls the generally accepted one, that the Beta was a way to put the new TR4 chassis under a TR3 body; Revington TR's opening line tells that story too, though its own page on the chassis doubts that the frame was a TR4's.

No record from the time has been read that could choose between them; each rests on recollection or on a later account.⁠source 2​source 3​source 1

The TR Drivers Club wrote in March 2015 that "both vehicles survive today". The black car, registered 917 HP, has belonged to Neil Revington since the early 2000s, and his firm has been restoring it; where the red car is, no source read says. A car built from Revington TR's panels and chassis of the Beta's pattern is a replica; only the two cars of about 1960 are prototypes.⁠source 1​source 2