It's the relevance rule, exactly, just the way they do it, and he compares it to Radio 4's Just a Minute:
You mustn't hesitate or deviate when speaking. The current rules mean it is impossible to speak for longer than four hours. I set the record for this century in 2005 when I spoke for three hours and 17 minutes, defeating a Tory bill to give householders more powers to defend themselves from burglars.
That doesn't mean householders in the sense we have here, which is the material that we distribute to our constituents by mail. He means people living in their homes. It was like a “my home is my castle” rule; you should be allowed to defend against burglars.
That was three hours and 17 minutes, debated on point, on subject, to make the point that a government bill was wrong. Now, that sounds really inefficient to me. If you go to the trouble of writing a bill, proposing a bill, getting consensus within your governing caucus, tabling the bill, and going through the motions of seeking support from everyday working people, only to then have a member being able to stand up and oppose it for three hours and 17 minutes and succeed, it sounds like a highly inefficient way of doing things.
To me, it also sounds like a way to honour Parliament, because there must have been an excellent reason for him to do that. He goes into some of the details on the difficulty he found in doing it. He says:
You are allowed to pause for three to four seconds, but it is risky to go any longer than that. Crossing your legs for the duration is essential.