Development of the upgraded version of the Tetrarch I under the designation of Light Tank Mk. VIII or A25 started in 1941. Its frontal hull and turret armor were enhanced and, together with the side plates, formed sloped armor. The vehicle's dimensions were unchanged, so its combat weight remained slightly over 8.5 tons.
In November 1941, the tank's name was changed to the Harry Hopkins I in honor of Harry Hopkins, President Roosevelt's advisor. The vehicle failed testing in the Middle East due to issues with thermal conditions and driving on sand. The first six tanks were built only in 1943, at which point they were of little interest to the British Army.
However, it is difficult to call the A25 project a failure. In 1942, the Alecto tank destroyer was developed based on the chassis of the Harry Hopkins I. It never saw combat but was used until the late 1940s in Europe and in the Middle East. One Harry Hopkins I vehicle has survived to this day and resides at the Bovington Tank Museum in the U.K.