Alternator light

Hi all
Just acquired a 2001 TD5 manual, on driving back (160 miles) the alternator light came on on the dash after 80 miles! I pulled over and checked the belt etc. without turning the engine off all ok. Drove it a further 80 miles with the light on and and no problems (it was day light so no lights etc) parked it on the drive and sure enough turned it off then tried to start it, wouldn't turn over! Looked at it just now all appears ok under the bonnet, tried the key started on the button, no alternator light!! all lights are fine, been for a 10 mile drive, no problems, no lights and starts first time multiple times! I'm confused (not hard) any ideas anyone? Cheers

could be the alternator getting hot?
or a bad connection on the alternator
or the bonding strap from engine to body/negative battery damaged..

without a diagnostic check of the system couldn't tell you for sure where the fault could be..

Thanks for that, at least I have somewhere to start.
Cheers

Just to let you know it turns out the alternator was filling with oil that was leaking out of the front cam shaft seal (you know the big black plastic plug on the timeing chain cover) so it would only do it on long runs. Changed the seal which has stopped the oil, cleaned out the alternator all appears good now. Fingers crossed.....