Dan Gurney had raced in Formula One since the late 1950s and, while at Brabham, joined with a group of American backers including Carroll Shelby and support from Goodyear Tire to form All American Racers. Inspired by the constructor-driver model of Jack Brabham and Bruce McLaren, AAR set up a British subsidiary, Anglo American Racers, based in Rye, East Sussex, which registered in the United States but built cars in Santa Ana, California.
To design the car, AAR hired ex-Lotus engineer Len Terry, who had just completed the 1965 Indianapolis 500-winning Lotus 38. His brief was to create a chassis suitable for both Formula One road courses and North American ovals. The resulting design closely followed the Lotus 38: a riveted aluminium monocoque with an unstressed engine mounted behind the driver. Suspension used lower wishbones and single top links at each corner, with inboard spring and damper units. The lines of the car were clean and refined, with a distinctive beaked radiator opening at the nose.
The car was conceived around a new 3.0-litre Aubrey Woods-designed Weslake V12 engine — the engine originally developed with funding from Shell Oil from a promising two-cylinder test unit. While the Weslake was being completed, the first Eagle Mk1 chassis raced with older 2.7-litre Coventry Climax FPF inline-four engines.
Four chassis in total were produced. The fourth, chassis number 104, was built from advanced materials including titanium components and a high proportion of magnesium sheet in the monocoque, earning it the nickname the Ti-Mag Car. Gurney was aware of the risk: after witnessing Jo Schlesser's fatal magnesium fire at the 1968 French Grand Prix, he compared racing it to "driving a Ronson cigarette lighter."
The Gurney-Weslake V12 developed around 360 bhp in its earliest form, rising to over 400 bhp by the end of the 1967 season — competitive with the Ferrari and Honda V12s and the newly introduced Cosworth DFV. Its distinctive high-revving exhaust note was immediately arresting. However, reliability was a persistent problem: the engine had been built using surplus machine tools dating from World War I, meaning tolerances and parts interchangeability were poor. A design flaw in the oil-scavenging system caused oil to pool in the sump, slightly reducing power after three or four laps of a race. Aerodynamicist Beatrice Shilling was brought in during 1967 to help address the issue.
The Eagle Mk1 debuted at the 1966 Belgian Grand Prix with Gurney at the wheel, finishing in Italian blue and white national racing colours with characteristic elegance but retiring from the race. At the 1966 Italian Grand Prix, the Weslake engine made its race debut, though Phil Hill failed to qualify in the older Climax-powered car and Gurney again retired. Points were scored during 1966 at the French and Mexican Grands Prix, but with the Climax-powered chassis rather than the Weslake.
For 1967 the Climax-engined chassis 101 was sold to Canadian driver Al Pease. All AAR entries ran as Eagle-Weslake machines. The season was intensely frustrating: despite Gurney and occasional teammate Bruce McLaren qualifying in the front two rows of the grid at all eleven rounds, only two cars finished a race all year. AAR's first win came at the non-championship Race of Champions at Brands Hatch, with Gurney winning in the aluminium-chassis 102. The team's sole World Championship victory came at the 1967 Belgian Grand Prix at Spa-Francorchamps, where Gurney drove the Ti-Mag car, chassis 104, to victory — the first Formula One win for an American-registered constructor since Jimmy Murphy's Duesenberg at the 1921 French Grand Prix, and still the only Formula One World Championship win for a USA-built car as of 2024.
By 1968 funding was running short, and development of the Mk1 ceased as resources were redirected toward the planned but never-completed Eagle Mk6 successor. Gurney persisted with the car through the first half of 1968 but achieved only retirements and a single ninth-place finish. AAR purchased a McLaren M7A for the remaining rounds, and it was with that car that Gurney scored the team's final championship points. At the end of the season, Anglo American Racers withdrew from Formula One.
The final championship appearance of an Eagle Mk1 came at the 1969 Canadian Grand Prix, when Al Pease privately entered chassis 101. Pease and the Eagle-Climax were disqualified for being too slow — the only car in World Championship history to receive that penalty.
The Eagle T1G's sole Formula One championship victory remained one of the most celebrated achievements by an American constructor in Grand Prix racing history. Its elegant, restrained design, the distinctive eagle-beak nose, and the distinctive Weslake V12 soundtrack cemented its reputation among the most aesthetically admired Formula One cars ever built. The basic Mark 1/Mark 2 chassis continued to be used in American National Championship racing into the early 1970s. Gurney himself clarified that "T1G" was never an official designation — the car was always the Eagle Mark 1.