The Valentine Mk I Archer was a British self-propelled anti-tank gun based on the Valentine tank chassis. It was equipped with a 17-pounder gun. There was almost no chassis that could accommodate such a large gun. The Valentine had a relatively small hull. As a result, it was not possible to use a revolving dome. Instead, the gun was mounted with the barrel to the rear in a simple open armored housing. So the barrel stands over the engine compartment, while the driver sits on the other side. The rear-facing gun seemed like a disadvantage at first, but it soon turned out to be an advantage. Combined with its low silhouette, the Archer (particularly from ambush) was an excellent weapon. The crew was able to fire a few shots and then drive off without having to turn.