With everything connected so that you're getting output from the alternator, but not running, measure the battery voltage. Start the engine and note what happens to the battery voltage.
http://www.gomog.com/allmorgan/LucasFault.pdf
Page 37\38 explain how it is wired & how to test. It is an ACR type ? not external reg type
It would seem you have a fault in the alternator or wired incorrectly, running the Alt without battery will do the internal regulator no good,
Look at the wiring in the Lucas crib simple checks
MOD Edit - fixed link. Page numbers refer to number printed on the page, not the PDF page number
Got it sorted. When I start the engine and the alternator spinner at the correct speed it all work. I was looking to far into it and finding fault that wasn't there.
Cheers for all the help though.