I have owned my Discovery for about 2 months now and have heard this squeaking in the mornings when letting the car warm up a bit.
Thanks
New landy owner
If the drive belt is the least bit slack, it will tend to skid and SQUEAL right after a cold start because the load and DRAG on the Alternator is very high as it tries to keep the system voltage up to par, about 14 volts or so.
Once the battery voltage is up, the alternator has less work to to, so the drag is less, and it tends not to skid and squeal.