Hi Snow I just been reading this thread and would like to try and clarify a little.
The small gear lever controls two separate but associated functions:
1. High & low ratios on the gearbox &
2. Locking the centre differential. This can be used in both high and low ratios. Move to left to put into difflock anda light should light up on the dashboard.
The centre difflock function is used in slippery conditions and what it does, when selected, it to apportion power equally to the front and rear axles.
This will not neccesarily stop you getting stuck. If you imagine soft stuff down the right hand side and firm stuff down the left, the front and rear diffs will allow drive power to the wheels on the soft stuff and so they spin.
Basic fundemental bad design - very few 4 wheel drives can lock all three diffs, the only one that comes to mind is the Merc G wagon.
The Japs approach this differently, they offten put a limited slip diff at the rear, to help with drive.
I love my Landys, but only being able to lock the centre diff, on a std 4x4 world renown vehicle, is crap !!!!