Now this could be fun, because tonight a trio of really disparate guests make themselves comfy on the sofa: Jack Dee, James McAvoy and drum roll Liza Minnelli! We know how much Norton loves a gay icon, judging by his glee at recent appearances by Bette Midler and Lady Gaga, but surely Minnelli beats them all. She talks about her life and career, of course, and also sings live. It will be delicious to see what she makes of Jack Dee, promoting a new series of his doleful sitcom Lead Balloon, in that often uncomfortable juxtaposition of a megastar and a cheeky British comedian they've never heard of (remember Maggie Gyllenhaal's bewilderment when faced with Russell Howard?). Bona fide Hollywood action man McAvoy (hasn't he come a long way since Shameless?) will discuss his role in the latest X Men movie, X Men First Class.

It would be unfair to say that Shameless (C4) has grown aimless because it was always about lives that lacked what might be called orthodox direction. When it began in 2004, with a cast that included James McAvoy, Anne-Marie Duff and Maxine Peake, one of the show's obvious charms was a manic, scattergun energy that refused to conform to any preconfigured narrative or moral shape.

Here was the underclass in all its feckless, drunken, irresponsible, irrepressible, resourceful, violent and promiscuous splendour, and there were no homilies or apologies or tales of transforming personal growth. After all the plastic melodramatics on EastEnders, this was a series that revelled in mundane minor victories over an absent landlord state: dole scams, housing benefit fraud, disability swindles.

What's more, in Frank Gallagher we heard the slurring, finger-jabbing voice of Asbo Britain. He was an antihero for our times, rat-like in his cunning and rat-arsed in his habits, a man whose waywardness made Yosser Hughes seem like Alan Partridge. Frank was a brilliant creation, not just emblematically but in terms of the story itself. His chronic dysfunction lent a tragicomic grandeur to the Chatsworth Estate.

The anticonscience is a tough act to maintain, however, and after seven years Frank's no longer just a drunken bore. He has also become boring. The show has come to rely on his ranting dereliction as a kind of dramatic prop, a lifeless symbol of continuity, like Ena Sharples's hairnet. And as Frank has become louder and more obnoxious, the other characters have also been sucked into caricature.

Last week the first five episodes of the new series played out on consecutive nights in a story that had Frank appearing in a variety of classic film and TV settings - Close Encounters of the Third Kind, Alien, Dr Who - but it turned out that he was drugged up in a psychiatric unit, where he'd been sectioned by his ex-wife Monica.

Yet even within the "reality" of the mental hospital, the film-makers couldn't resist pastiching One Flew Over the Cuckoo's Nest, with Frank recreating Jack Nicholson's role as the rebel patient Randle McMurphy. In fact all five episodes were awash with hallucinations and dream sequences, a disorienting prospect at the best of times, but deadeningly exhausting over the course of a week. It was as though jumping the shark - the moment at which a long-running TV series collapses into absurdity - had been turned into a marathon sport.

Everything about the new series - from the surreal film references to the relentlessly transgressive plotlines and the coarse, preachy tone - spoke of a frantic desperation to be meaningful. In seeking to demonstrate an urgent sense of purpose, Shameless may not have lost its aim, but it has lost its point.

Paul Abbott's ribald comedy-drama about the Gallagher family has been a breeding ground for strong British acting - James McAvoy, Maxine Peake and Anne-Marie Duff have all inhabited its Chatsworth estate - and the series continues to bring the novelty. The first five episodes of this eighth series are stripped across five consecutive nights, so if you've dropped out of the habit of watching, and feel Frank's errant dynasty has become too complex to follow, here's an opportunity to catch up. And what better way to start than with the wedding of the year: Frank's. But, er, where is he, exactly?

James McAvoy and Hugh Laurie sign up for Aardman film

James McAvoy and Hugh Laurie have joined the voice cast for Arthur Christmas - the latest film from Aardman Animations.

Hugh Laurie signs up for Aardman film

Hugh Laurie and James McAvoy have joined the voice cast for Arthur Christmas - the latest film from Aardman Animations.

This charming romantic comedy set in 1985 stars James McAvoy as a working-class lad from Essex who uses his place at Bristol University primarily as a way of achieving his dream of appearing in the final of University Challenge. On the way, of course, he falls for a team-mate (Rebecca Hall) and rows with his mother (Catherine Tate).