"i was under the impression directors could buy based on insider knowledge"
I'm of the opinion that if a Director is buying/selling without insider knowledge then perhaps he's not the best bloke (or lady) to be running the show...
Surely it would be pretty hard to be a Director, have access to everything up to date by the minute and not have some inkling of futre SP?!
Like someone else said - hopefully he's not buying in just for the fun of it!