It is not a Humber Box 4x4, ...it appears to be a military Humber Snipe 2 wheel drive chassis, with 900x13 tyres, there were military Woody utility estate versions, but this is not a military body, more likely its been rebodied post war with a longer and higher civilian coachbuilt 2 door body, the military Humber utilities were 4 door and used the steel bulhead and windscreen of the Snipe car as show in the photo below