house of commons

I was watching questions for the PM and noticed three or four people sitting together in the House of Commons wearing wigs and robes. Can someone tell me who they are? I've tried searching but apparently don't know the right question to ask. I understand the Speaker used to wear a wig and a robe...

Apologies if this has already been posted here (I couldn't find it), but I have signed up to this pledge. It's half way there, so there's a good chance of meeting the target. I think it's worth doing.