Strange noise after long drive, near driver side rear wheel

[evo]

So the other day, went on a long drive to London, around the town, up to Surrey and around the country roads there before heading back up to Birmingham. All was well, no problems to report.

On getting back to Birmingham and parking in my driveway, as I got out there was a strange whirring noise, as if some kind of motor that felt like it came from the driver side rear wheel... lasted about 6-8 seconds then was off.

Never been able to reproduce it since, and no idea what it could be. I don't engage the parking brake often, and I didn't engage it at this time I parked up either although the noise was similar from inside the cabin, but much louder as I was stood outside the car.

Any ideas? Anyone had this before? Should I be worried?

2008 D3 3.0 TDI...