Just *what* kind of grenade did that guy have, anyway?

In regards to the recent incident at Gatwick Airport in the UK: just what kind of grenade was the guy caught with? Every report I’ve seen says that it’s a live grenade, but not what kind. Given the general ignorance of the popular press in such matters, I wouldn’t be surprised to find out that it was a (live) smoke or tear gas grenade.

Anyone know?