QI (BBC1, 9pm); Rocket Science (BBC2, 9pm); The New Avengers (BBC4, 12.10am); Al Murray’s Multiple Personality Disorder (ITV1, 9.30pm)

QUIZMASTER Stephen Fry is joined by two of his best buddies in this week’s QI.

It’s a real luvvie fest, thanks to the presence of John Sessions, who’s appeared on the show several times before, and first-timer Emma Thompson.

She and Fry go way back, of course.

They met at Cambridge, and were members of the famous Footlights troupe, which also included Tony Slattery and Hugh Laurie. They’ve appeared on screen together in such projects as Alfresco and Peter’s Friends.

Friday evening may be the traditional place to find QI in the schedules, but a growing number of regular viewers are turning to Saturday’s XL (that’s extended, to you and me) version of the show.

When it first began, nobody really thought there was much mileage in a quiz in which the questions were, by and large, too difficult to answer.

How wrong they were, or at least how they forgot that Fry can make even the most mundane subject sound as if it’s the most interesting one in the world. He has a sense of wide-eyed wonder when it comes to facts, even though he probably knows about 90 per cent of the stuff mentioned on the show anyway.

As for the rules, listen to Fry’s explanation in the first series. “Now, the rules are simple. Scoring is my business. Points are given and points are taken away. They are taken away for answers which are both obvious and wrong, and they’re given, not so much for being correct, as for being interesting.

“Their level of interestingness is impartially determined by a demographically selected customer service focus consultancy, broken down by age and sex – ie me. Because there is no one more broken down by age and sex than me.”

Rocket Science follows the efforts of science teacher Andy Smith to demonstrate the pleasures to be had from his subject. With the post-GCSE take-up for sciences down 25 per cent, the pressure is on this educator to prove his passion to Woodchurch High School’s Class 8XS.

His plan is to use the world of fireworks to ignite a similar love of chemistry and physics in his students, and he begins in this opener by roping in an expert to set up a display. Alas, the whole thing’s a bit of a damp squib and leaves most of the 13-year-old audience turned off.

Smith wins the pupils over with an innovative glow-in-the-dark lesson, and by the time the class leave, they’re all hugely enthusiastic.

So, Smith resolves to give them a project that will fuel this new-found interest in science. He plans a firework display to mark the head teacher’s retirement. Alas, not everything goes to plan.

As any fan of cult TV will tell you, classic Seventies series The New Avengers was a game of two halves.

The first run was a London-based series of outrageous escapades involving giant rats and plots to resurrect Hitler. However, the second run was a hit-and-miss affair, especially during episodes filmed in Canada. The same cast was present, but the series lost some of its offbeat charm.

THIS is one of the best offerings from that second run, and involves a large number of civil servants, MPs and intelligence personnel dying from apparently natural causes. There’s no link between them, until a British agent mentions the “angels of death”.

Aside from regular stars Patrick Macnee, Gareth Hunt and Joanna Lumley, the supporting cast includes comedienneturned- psychologist Pamela Stephenson, cult movie glamourpuss Caroline Munro, and Lindsay Duncan.

Comedy sketch show Al Murray’s Multiple Personality Disorder features the man from the Pub Landlord, alongside such larger-than-life characters as Prurient Dad Peter Taylor, an embarrassing West Country father; the silver-tongued Victorian gentleman-thief Barrington Blowtorch; Horst Schwull, Hitler’s most trusted aide, who is just a little on the camp side; and Gary Parsley, an outrageous, over-demanding, piano-playing Seventies rock star.