What does this mean?

[WhatchaMaCalllit]

When the Speaker of the house says the result of a vote in the House of Commons, he finishes with "Unlock" - what does that mean?

They lock the doors of the lobbies. I suppose it's to stop people running around and voting again. But what I don't understand myself, is how they all get out again to see the result, if the doors are locked.

Is that where the term 'lobbyist' comes from? They are supposed to meet and discuss and sway the decision of politicians in the lobby before a vote???

I'm genuinely interested as these are terms that I've heard in general conversation but never really understood the background to them.

Lobbying has its own Wikipedia page OP. en.wikipedia.org/wiki/Lobbying