[Richard Coutts-Smith]

The Humber One Ton has a similar Fuel Tank set up. Only the drivers side has a gauge, and even more of a surprise, the change over tap is on top of the tank, ie outside the cab.
From personal experience, running off both tanks in off-road conditions can lead to all fuel being in one tank, and sucking air out of the other.
Most interesting vehicle Gordon, am enjoying your updates.
Rich.