In order to better provide artillery support in the highly mobile desert warfare of the North African Campaign, the British Army had quickly adapted the Valentine tank into a self-propelled 25-pounder gun: the Bishop.

In particular, limited space meant that the turret had little elevation, requiring crews to use natural slopes, embankments or mounds to get the full range out of the gun.

As a stop-gap, the US-built M7 Priest, with a M101 105 mm howitzer, mounted on a M3 Lee chassis, was soon replacing the Bishop, reaching service in October 1942.

[3] However, because the US 105 mm gun was not otherwise used by the British military, supplying ammunition to Priest crews was complicated and caused delays.

Development was delayed by issues including the destruction of the gun mount on the prototype, during the first live-firing trials.

In May 1943, it was formally accepted for use by the British Army and given the name "Sexton" (after the religious custodian and following in the tradition of the Bishop and the Deacon self-propelled guns).

A UK order for 300 Sextons was made in mid-1943, albeit built on the hull of the Grizzly tank (a Canadian-built variant of the M4A1 Sherman).

In spite of its confused origins, the Sexton was a combination of proven parts and proved to be a successful design that remained in British service until 1956.