Hello, and welcome to the forum.
The manual I referred to in Tom Watts's thread (
MANUAL), shows the TL110-L5 as originally having 10.50-16 tyres front and rear (to Contract SM 2458, dated 30 Jun 42, co-incidentally shown in "Light Stone" or sand paint). It was common practice in post-war Australia (and I suspect Britain would be similar) to fit dual wheels to the rear of many War-surplus vehicles to increase the legally allowed capacity of the truck in civilian service.
Bedford and Austin truck duals have the same wheel stud pattern as the WD single wheel, and are a straight swap on the rear axle. As a dual wheel rim has a different "offset" to a single rim, they must be fitted with a spacer (or a different design hub) on the front axle to maintain steering geometry, but on a 4x2 vehicle any variation in tyre diameter isn't as critical as on a 4x4, so often it was simpler to keep the original wheel on the front axle.