Car won't crank on 2000 Jaguar XJ8

My 2000 Vanden Plas won't turn over. I parked the car, which had never exhibited any similar issues in the past, and when I tried to crank it again, 8 hours later, it wouldn't start. The battery is good, and the instrument panel lights up, but when I turn the key, nothing happens. Any ideas or suggestions would be appreciated.

Asked by for the 2000 Jaguar XJ8
You may have a bad starter or ignition switch.