A question about supposed 7/7 suicide bomber and McDonald's?

It was reported and there is CCTV ffotage of Hasib Hussain one of the supposed 7/7 bombers that he went into McDonalds just before the bombings and ate a beef burger. My question is why would a fanatic islamist millitant eat a beef burger in McDonalds? Don't muslims only eat halal meat? If he really was a devout follower surely he'd know the basics of his religion?