I had a similar issue on my 200tdi- see third pic for possible cause....
https://www.landyzone.co.uk/land-rover/2-5n-a-to-200tdi-conversion.168563/post-1733336
I've used a crow bar to tension a belt, a long time ago.
The charge light came on when I started it up and went away when I subsequently slackened it off a bit.