Tellers

Ian Mearns helpfully points out the tellers, lined up before the Commons Table.

Every time the Commons divides, four tellers are appointed to count the vote, two for the Ayes and two for the Noes. They are usually party whips or the leaders of internal party factions like the CBCJS who are informally whipping a dissenting vote. The tellers report the results of the vote back to the Chair, who then announces it to the House.

Miscounts

The announced vote is binding regardless of how MPs actually voted, so the tellers have a lot of power. If they happen to miscount either by accident or on purpose, the miscounted vote will be recorded. That's why there are two for each side- one goes into the opposing voting lobby to make sure there's no funny business. Miscounts can occasionally be of historic significance. The bill establishing the important civil right of habeas corpus was only passed because the Ayes teller counted a fat Lord as 10 votes for a joke and the teller for the Noes failed to notice in time.

The Lineup

When the tellers come in they line up in front of the Commons Table to announce the vote. The tellers for the majority always stand on the right-hand side (the Speaker's left), which makes it possible for the House to tell how a close vote has gone before the official result is announced. Sometimes this leads to hilarity or confusion:

• In the 2013 vote on military intervention in Syria, Tory whip Mark Lancaster played a rather cruel trick on his own party by refusing to line up until the other lobby had reported. This briefly misled Government MPs into thinking they had won the vote, and there was shock on the Government benches and a jubilant riot amongst the Opposition when the tellers from the second lobby came out and the true outcome was revealed.
• In the 2015 plot to oust Bercow, a Tory got his left and right mixed up and heckled Bercow, thinking that the order of the tellers meant the coup had succeeded. Labour were happy to set him straight.