Some episodes of QI are quite funny, others are quite interesting. The best episodes combine the two to become extremely entertaining, but I think "Gravity" will have to settle for quite interesting. Actually, make that very interesting. This was one of those episodes where the sheer wealth of astonishing trivia overshadowed the jokes because the guests were hanging on Stephen Fry's every word. Ordinarily, I'd grumble about them being paid to sit there as glorified members of the studio audience, but I actually don't blame them because I was similarly fascinated...

Regardless, it was a shame Rich Hall didn't make much of an impression here, as he's ordinarily good value as the laconic interjector, but my low expectations for QI newbie Barry Humphries were proven well founded. He's only ever funny in the guise of his alter-ego Dame Edna Everage (and even the hilarity of Edna's debatable), and his lacklustre performance here proved so. Humphries' garish clothes were the only thing memorable about him. So yes, we'll have to put this episode down as a something you'll find yourself enjoying mainly for non-comedic reasons. I'm still fascinated by the fact it takes 42-minutes to fall through the Earth's surface to any point on the planet (be it London to Australia, or London to Paris), and that the bullet from a gun fired while aimed parallel to the ground at arm's length will hit the ground at the same time you simply drop a bullet held at the same height.

The frustrating thing about QI is that it's increasingly difficult to impress people down the pub with the littleknown facts it throws up, as it's become so popular (and it repeated so often) that your source is always never in doubt.

Just having something to laugh at in these grim times is enough. As Rich Hall said on 4 at The Fringe, "When people are happy comedians suffer." True enough, but Radio 4 listeners have sat through enough dire comedians to know some depths of suffering for themselves.

This show, the first of two, served up four acts from this year's Edinburgh fringe, all of them established and familiar. In fact, Fred MacAulay is so familiar we're almost related. Yet his style of observational comedy is really funny (budget airlines, dogs taking over from children as sofa occupants) and his timing is flawless. That, I suppose, comes with experience.

When it flies, stand-up comedy is an exhilarating experience, and this - the first of a new series of Live at the Apollo - is a spectacularly good example of the genre. It is introduced by Michael McIntyre, who minces around the stage exploding with energy ('When I smile,' he asks, 'do I look like a fat Chinese man?' Yes, Michael, you know you do). He is followed by Rich Hall, who describes how an Englishman loses his temper ('I shall write a letter!') and how he met the Queen at Buckingham Palace. And it ends with an insane performance by a Welshman, Rhod Gilbert, who has a high-octane nervous breakdown trying to buy a duvet. If even a tiny part of you enjoys stand-up, you don't want to miss this.