1998 4.0 Sovereign, 110k miles. In case it's of any help to others, this is what happened. Started the car as normal, no problems. Immediately the System Test went out, it came up with three alternating warning messages: Gearbox fault, Traction Control Fault, Stability Control Fault. The airbag light also came on, the check engine light came on, the wipers or indicators wouldn't work and the dash lights went out. Hmm, not so good. The vehicle only had 4th gear and reverse.

Unfortunately, I had no choice but to drive a twenty mile return journey, not overly pleasant. On my return, I went to the battery to do a hard reset, the battery and the earth strap were quite warm to the touch. Checked the voltage at the battery with the engine running at idle, it was 16.4V.

New alternator fitted, all back to normal and hopefully, the six-month old battery wasn't damaged by the heat.