Where does "three line whip" come from?

In parliament a three line whip is said to be applied when a party seeks to ensure every MP turns up and votes the party line.

But why the term "three line" whip? And is there such a thing as a one or two line whip?

Solution 1:

There are indeed one and two line whips - they basically boil down to how strong the expectation to vote is.

A single whip is simply a guideline, while a double whip (or two line whip) is stricter - and attendance at the vote is required. The three-line whip is a 'vote with the party or get out'.

The number of lines comes from the number of times that a vote is underlined by the Chief Whip in the parliament's schedule.