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They manage to convince MPs to vote in certain ways, perhaps with a little flattery, an overseas trip or hints of preferment – but also warnings that failure to do the right thing could damage their career.
And of course there is the little black book where whips store up information about MPs' affairs and indiscretions which might be useful at a later date.
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But the veil shrouding the whips’ activities was ripped open last week when Tory backbencher William Wragg accused them of using blackmail.
And he was backed up by Bury South MP Christian Wakeford, who had just defected from the Tories to Labour. He claimed former Education Secretary and one-time chief whip Gavin Williamson had threatened he would lose funding for a new high school in his constituency if he did not vote with the government.
There were also reports of whips spreading rumours about Mr Wakeford's personal life immediately after his defection.
The blackmail claims have been rejected while senior politicians have insisted the traditional image of the whips no longer reflects reality and such behaviour would be unacceptable.
But some older MPs are dismissive of the complaints, implying it's just the way things work and people had better get used to it.
One former minister noted the allegations were coming mostly from newer MPs and branded them “snowflakes”.
Despite the secrecy, there has been enough evidence over the years to establish a history of murky goings-on.
Willie Whitelaw, Conservative chief whip in the 1960s, confirmed the practice of keeping a “dirt” book. "The dirt book is just a little book where you write down various things you know or hear about people that may or may not be true. I think you could make a very good guess what sorts of things it contains."
Tim Fortescue, a whip in the early 1970s, said MPs who found themselves in some kind of scandal might turn to the whips for help. "We would do everything we can because we would store up brownie points… and if we could get a chap out of trouble then he will do as we ask for ever more."
And another MP recalled how whips had worked in the the early 1990s, when John Major was battling against Eurosceptics. "They would try everything – threats and inducements – saying they knew things that they didn't want to have to make public. With some it was affairs, or things like visits to gay nightclubs. It didn't matter if it wasn't true.”
And Tory MP and former whip Michael Fabricant has said: "If I reported every time I had been threatened by a whip or if a whip reported every time I had threatened them, the police wouldn't have any time to conduct any other police work."
The whips' tactics may be explained away as an integral part of the political system. But remember how MPs’ expenses went unquestioned until the abuses were exposed in 2009.
Once open to public gaze, a feature of Westminster life which had been taken for granted was suddenly recognised as unacceptable. Perhaps sunlight might yet again prove to be the best disinfectant.