By Brian Wheeler
BBC News politics reporter
It is a sacred rite, as old as parliamentary democracy itself.
The man from Henley, he says yes...and no
After debating all sides of an issue on the floor of the House of Commons, MPs dutifully file out of the chamber to vote, normally dividing down party lines into the 'aye' and 'no' lobbies.
If they feel strongly enough an MP might rebel against their party's line and vote no when they should be voting yes, or vice versa.
But what if they can't make up their minds? Or they want to say 'yes' to some bits of the legislation but 'no' to others?
If they are Conservative MP Boris Johnson, who faced just such a dilemma on Wednesday, they will vote in one lobby with their party colleagues...and then nip back round and vote in the other.
The Henley MP's latest wheeze came about because Tory MPs had been ordered to vote with the government at this stage of its anti-terror bill's passage through parliament.
Mr Johnson did not agree with the bill's more controversial aspects, which include detaining suspects without charge for up to 90 days. But instead of abstaining, he decided to register his dissent with both a 'yes' and a 'no' vote.
"It was the best way of summing up my feelings about the Bill.
There are good bits in it but I am deeply opposed to the two measures that are most controversial," he told reporters afterwards.
The speaker's office says there is no rule against voting in both lobbies, although a spokesman said they do not like to encourage it.
A spokesman for the Commons library said: "MPs usually do it because they have changed their mind or made a mistake and they want to annul their vote."
But Mr Johnson is not alone in his fondness for going through both lobbies. In fact, compared to Labour's David Taylor, he is a yes/no novice.
The North West Leicestershire MP has voted both yes and no on 25 separate occasions since being elected to parliament.
He admits his actions have "perplexed" Labour's whips, who are responsible for party discipline and maintaining the government's majority.
And some of his party colleagues have not been too pleased with the tactic either.
"You are open to criticism. But the moment you start being sensitive to criticism in this place you might as well pack up and go home."
'Black and white'
But Mr Taylor insists going through both lobbies is the only way to formally register his abstention from a vote.
"It is not a question of vacillation or indecision. There is a lack of opportunity to register an abstention in this place, in a way that is recorded," says Mr Taylor.
On some issues, such as the government's incitement to religious hatred bill, Mr Taylor wanted to register a "positive abstention".
At other times, such as reform the House of Lords, Mr Taylor agreed with some parts of the bill but not with others.
"Some issues are not black and white, as much as the media would like them to be," he says.
He says there should be a "mechanism" for registering an abstention, "because otherwise it looks like you were not present."
Mr Taylor says he has no preference when it comes to which lobby he goes through first, but he has a few tips for MPs wishing to follow his example.
"You have to go through the first lobby fairly quickly because you have just eight minutes to vote.
"It's not just a matter of tip-toeing through the Tories with a mask over your head and then going to sit with your friends on the Labour benches as if nothing has happened."