The official who actually knocks on the door is the "Gentleman Usher of the Black Rod", or "Black Rod" for short.

Quite what else he does is mystery to me. One celebrated holder of the post was the former Lieutenant-General Sir Brian Horrocks. He always appeared to be very busy with paperwork at his desk in front of the Lord Chancellor. In his memoirs he admitted that he was actually whiling away the time by doing his football pools.

HM is never actually allowed into the Commons; which is why the MPs have to troop into the Lords to hear her parrot the Queen's Speech. The last monarch to burst into the lower chamber was Charles I, who was trying to arrest 5 recalcitrant MPs (Pym, Hampden, Holles, Hesilrige and Strode). He was trying to forestall a Civil War; this action helped start it.

I am not too sure whether the recent reform of the Lords, from a hereditary house to an almost wholly-appointed one will make much difference to UK politics. I am reminded of a line from the comedy program "Yes, Minister" (which starred the late actors Paul Edington and Nigel Hawthorne), commenting on a minister who has fallen from grace. "Well, he was apparently as drunk as a Lord last night. So, after a decent interval, I suppose they will make him one".