After my 1.9 TDi SLX has got warm and has been running for a while, quite often I et a high pitched whine (almost a squeal) from *I think* the rear near side wheel.

If I apply the brakes (even with only a little force) the noise stops, but as soon as I lift off it's back.

I thought maybe when the disks got hot, something was rubbing, but I couldn't see any warping in the disks or pads or anything.

Anyone got any ideas?

wheel bearing?

jack it up and give it a wiggle and see if there is any play in it. Someone once suggested spinning the wheel and holding the spring to see if there was any vibration (not tried that though)

Does it stop if you lightly apply the handbrake? Are the brake calipiers getting hot? Could be a small piece of grit rubbing on the disc - are there any scratches/grooves on the discs?

Was going to say that you shouldn't leave the missus in the boot but that's just cruel :P

Wheel bearing seconded and ditto for making sure the handbrake isn't dragging.

If you can't find anything try putting a bit of copper grease behind yhe pad see if it's just a vibration.