My 2001 xk8 when left overnight will not start. New battery installed. When I take the key out the radio stays on and has to be turned off manually. There is also a whirring noise in the boot for a few minutes after key removal.
Any ideas much appreciated.

Thanks graham

 

Possibly the ignition lock sticking.

The whirring noise in the boot being from the Security Module after the chip in the key is out of range of the ignition barrel Exciter Ring (key transponder).

Graham

 

i think the whirring noise could be the antennae re-tracting