The most important thing to check would be the engine for internal corrosion. Even if there isn't any you would need to ensure that oil was applied to the various working parts before attempting to start it. Inject oil into the big end from the quill in the timing cover , timing gears , cams etc , rocker's and top end , few squirts down each plug hole the day before starting so that it can seep around the rings. Has it ever been registered ?
Thanks for the suggestions.
As far as starting the bike i do intend to check for corrosion where i can also to put oil down the plug holes and drain and refil with new oil. Then i was thinking of leaving the plugs out and bumping it down the hill he lives on a few times prior to thinking about firing it up.
It has never been registered. The bike was bought in a kit as described in the pictures of the brochure but my dad never finished it off so has never even been ridden on the road. It has 0 miles on fully rebuilt and refurbished engine and all the other parts were bought brand new all receipts are there to prove and are dated. The only ride it was ever used for was in 1979 when we moved house when my dad literally took it up the road and back probably 200 yards max. Since then it has been in the back of the garage all covered over and untouched.