So today, I managed to get myself stuck on a pile of snow. I was well and truly not going anywhere so I had to get my husband to help me. He noticed that only one back wheel was spinning. So he seems to think that I do not have 4 x 4 capabilities. I insisted that land rovers were permanently 4 wheel drive. Who is right? And why would only one wheel spin? The other back tire was on frozen ground, the front ones were on the road. I couldn't engage the diff lock as the lever is seized. It's a discovery 1.

 

Without the diff lock engaged on the center diff you have 3 open differentials. So the power will take the path of least resistance. Which would be the one spinning tire.

You do have full time 4wd but with 3 open diffs until you fix the shifter. Than at least you can spin two tires.

 

Yea, you need to fix the CDL.

 

In an 'open' (not locked) differential, power travels to the wheel that will spin most easily.

 

My CDL was also jammed. The safety actuator failed and wouldn't allow the lever to move. I removed the actuator lubricated the linkages and it works fine now.
It seems like a common problem

 

Basically the Disco is full time AWD, while the wheels maintain traction/contact with the ground. When you lock the center diff it becomes 4WD. However, if you get cross-axled and one front/one rear lose traction you won't go anywhere.
Locking the center diff makes a world of difference.