The Cruiser Mk I (A9) was designed at Vickers Armstrongs in 1934 by Sir John Carden. Initially the Cruiser Mk I was to support the Vickers Medium Mk IIs but it soon replaced them. He designed it during the depression and the design had many cost cutting measures.
Much of the armor was vertical and many angles for shots to get trapped in.
The driving and fighting compartments of the Cruiser Mk I were located together.
Each of the machine gun gunners were on each side of the driver in turrets.
The original engine was a Rolls-Royce car engine but it was underpowered and an AEC bus engine was substituted.
The steering brakes were mounted on the outside of the rear sprockets. This allowed them to cool faster.
There was an auxiliary engine that was used to start the main engine, charge the batteries, and drove a fan in the fighting compartment.
The suspension was later used on the Valentine with some minor modifications.
Had a Nash and Thompson hydraulic powered turret traverse, which was a first for British tanks.