I have an XF-S to UK spec. 2013 model, mileage 3,500k If my car is parked, nose down on a medium grade slope, engine off, when returning to the vehicle I find that after starting the engine and trying to reverse, say out of a tight car park, that the brakes are locked. There are no dashboard indications to confirm this. That is to say the handbrake symbol is not on. Pushing down the handbrake lever has no effect. As you can imagine it's most disconcerting! Engine revs high, sudden reverse jump, and a million dollar R.R. just 1.5m behind you! Help!