The Valentine began life as a private venture by Vickers-Armstrong as an infantry tank, but one that shared numerous components from existing cruiser tanks. Indeed the appearance of the Valentine approximated that of a cruiser tank most, but had substantially stronger armor which limited its mobility. Its main drawbacks were a small turret which was either cramped with three crew members, or led the crew being overworked in those marks with only two (commander and gunner). As was typical with most British tanks, it was also poorly armed; initially with a 2-pounder that was all but obsolete even when the war began, and later with a still inadequate 6-pounder (only in its final mark was it up-gunned with a 75-mm gun). On the positive side, the Valentine was mechanically reliable and gave a good account of itself in the long distances and difficult conditions of the North African theater where it was most of its combat. A few were also used by Commonwealth forces in Burma and the Pacific, and although it had been superseded as a tank, it served in non-combat roles in Northwest Europe after D-Day. Production was undertaken in Canada as well, and it was supplied extensively as part of Lend-Lease where the USSR received as many as 45% of all British and Canadian-built Valentines despite their inadequacy for combat on the Eastern Front. Some were upgraded with Soviet 76.2-mm guns to improve their combat effectiveness.

The Light Tank Mark III Valentine was conceived before the war, it's name arising from the date in which the design was submitted to the War Office: 14 February 1938. Orders were placed in mid-1939 with the first delivered by May 1940 but did not see combat until the North African campaign in 1941. The original Valentine Mk. I was equipped with a 2-pounder gun and powered with an AEC gasoline engine. This was replaced by a diesel in the Mk. II, with desert units also fitted with sand shields and fuel tanks (those fitted with GMC diesels were known as Mk. IV). The Mk. III added a third crew member, an improved mantlet and a commander's hatch but some retained the old turret and were designated Mk. V. The Mk. VIII added a 6-pounder gun to the Mk. III, giving it a more powerful punch, and reduced the turret crew to two, while the Mk. IX was a similar upgrade to the Mk. V. These all had the co-axial gun deleted but this was retained in the Mk. X which also had an uprated engine. The final variant was the Mk. XI with a 75-mm gun and of welded construction. Non-tank variants included the Valentine OP/Command vehicle, as well as other roles including mine-sweepers, bridge-layers, flame mortars, anti-tank mounts, flamethrowers, roller fascines, and a DD (Duplex Drive) amphibious variant. Aside from the first, the remainder were not used operationally, in many cases due to the fitting of the same equipment into a Sherman or Churchill chassis.