I hate to tell you but i think your engine fell out. But Halfords have some great additives which can work miracles with older engines, I'd get all of them mix them up in a bucket, stick them in, and see what happens!
I know people don't like to pamper their Landies too much, but I think that could use a wash and brush up too, particularly in the engine bay, it's in danger of getting a little debris/ detritus, which may cause issues! Maybe a jet wash under the bonnet?