I'm not sure that we've got any nearer deciding what the small cloth patch immediately below the collar at the rear of the officer's jacket stood for, though I bow to Tankertrashnav's superior knowledge in these matters that it indicated the formation (Brigade, Division?) of the wearer.
It was so small that it would have no tactical value, even on the ground let alone from the air. If it did indicate the formation, then it would have been common throughout the British Army then, surely? I've never come across it before. Could it have been a "Sherwood Foresters" device? Certain Regiments wear a cap badge front and rear because of heroic past deeds. Could this be such a regimental historical device? Like TomJoad, I've no idea but I bet someone here does, or knows someone else who does...