1972, in fact!
See below link . . .
http://www.skyscrapercity.com/showpost.php?p=63356797&postcount=114
Been refurbished a fair few times since 1972, mind.
Interesting article!
Very glad that they didn't have a stadium built all the way around like the East Stand mind
Saying that i quite like the East Stand, it adds a bit more character to the ground
I've never been able to find a picture of the old East Stand on Leazes Terrace either which was interesting
http://i698.photobucket.com/albums/vv345/manorpark_photos/1972PlansforStJamesPark008.jpg