Sounds more like it lost synch with the car's immobiliser.

There's two components in a late Xant's key.

Firstly, the remote locking. That uses a battery.
Secondly, the immobiliser. That doesn't - there's a passive transponder in
there which is powered by induction from the sensor in the steering column.

I suspect your friend's father's key problem was the latter.

Change the batteries in the key every handful of years, and you'll be fine
on the former. My own '96 XM has the same batteries in the key now as it
did when I bought it in '00 - and I doubt they'd been replaced before then.

There is a battery in the fob to operate the remote locking. If this went
flat, as it will after an extended period, it will cost the exhorbitant sum
of less than £3 to replace. All car spares places stock them, as do many
larger supermarkets. To open the fob insert a knife blade between the halves
where the key ring attaches and twist. If there is a screw holding the metal
key into the fob then that should be removed first.
There are several types of battery, just check the number on the one in
yours to ensure you buy the correct replacement.
Of course you can take it to your dealer to get this done, and pay them many
times more for the service.