Trojan never built anything bigger than their post-war chassis-less 1-ton van, which you will remember in its Brooke Bond livery (did anyone else buy them?!) It went out of production when Trojan ceased to exist in 1959.
But they started out in 1924, when their vans were built by Leyland Motors in Kingston upon Thames.
They only built 5 cwt, 7 cwt and 10 cwt vans before WW2 so the puzzle vehicle must be based on one of their 1950s 1-ton vans, and continued the Trojan tradition of making pug-ugly vehicles...!