I'm afraid Debra Stephenson's impersonation of The X Factor's Tulisa shows few signs of improvement (which is why Jon Culshaw's Louis Walsh has to keep addressing her by name).

To be fair, though, Debra's Claudia Winkleman (in her role as host of Film 2011) is still hilarious. Tonight we get Claudia's attempt at reviewing the new Tintin movie.

It's rare to find impressionists whose material matches their talent but for most of this enjoyable half-hour programme Jon Culshaw and Debra Stephenson have pulled it off. Both find moments to shine. Culshaw nails fashion consultant Gok Wan's slangy lingo and makes a suitably narcissistic Elton John. Stephenson shows us what it would be like to be stuck in a forest with Kirstie Allsopp and excels with her uncanny take on a breathless squinty-eyed Claudia Winkleman.

What happened to impressionists? There was a time when it was the blue-chip form of light entertainment, and no weekend or Christmas was complete without a special. But the steam seems to have gone out of it a little these days. The Impressions Show has its moments (Debra Stephenson gets that mad vamp off Dragons' Den to a T and Jon Culshaw nails Paul McCartney and Prince Charles). But all too often if you close your eyes you wouldn't have a clue who was being lampooned. It gives an impression of being entertaining, but not always a convincing one.

Jon Culshaw and Debra Stephenson offer up another 30 minutes of pretending to be other people. When the show hits home, as in a MasterChef skit where John Torode and Gregg Wallace reckon the contestants are "like cows at an abattoir", there's much fun to be had. Paul McCartney reforming the Fab Four with "all of the surviving Beatles except Ringo" and the Gok Wan wok gun also hit the mark. At other times, though, don't be surprised if your attention drifts: the show is consistently inventive without necessarily being consistently funny.

The Impressions Show saw Debra Stephenson miss two open goals with Hilary Devey and Tulisa. But with her physique, her Mary Portas, Claudia Winkleman and Fiona Bruce were exactly like the real thing - only foxier.

Jon Culshaw on the other hand was such a car crash his impersonations were more fascinating. His 'Bruce Forsyth' was bang on - if it had been Alex Ferguson, while his 'John Bishop', was the spit of Laurence Llewelyn Bowen. Final score? Debra Stephenson 5 - Jon Culshaw 0.

Don't expect any Eamonn Holmes jokes in this series.

Last year the BBC had to issue a formal apology after sketches showed him eating the studio furniture and he took the view that imitation wasn't the sincerest form of flattery at all.

But Eamonn would be old news anyway, in impression terms. The key here is topicality, and Hilary Devey and Tulisa are just two of the new faces as Jon Culshaw and Debra Stephenson return for a third series.

The pair are superb mimics and it's a pleasant half-hour ticking off all the celebs you recognise.

Culshaw completely nails the way former MP Ann Widdecombe's voice keeps wandering off into that strange falsetto and Stephenson's Alex Jones is spot on.

It's just a pity the writers aren't keeping up their end of the bargain by giving them funnier material to get their teeth into.

Jon Culshaw might not be the best mimic to have graced the small screen, but he still knows how to serve up an enjoyable half hour of comedy as his Impressions Show returns for a new series. The real star here though is Culshaw's altogether more impressive co-star Debra Stephenson, whose take on Claudia Winkleman is worth tuning in for alone.

Impressionists Jon Culshaw and Debra Stephenson are accomplished performers but their material struggles to match their talent. There's fun to be had in the unlikely relationship between chirpy John Craven and Stephenson's deadpan Lady Gaga, but yet another send-up of Simon Cowell's taste in trousers is just lazy.

Any sketch show is bound to be a hit or miss affair, but the celebrity parodies done by Jon Culshaw and Debra Stephenson are so amazingly accomplished, you can forgive the odd item that doesn't quite work. There's an ongoing gag threading through the show about how Katie Price is marrying Michael Winner, while Culshaw's take on Harry Hill as a UN peace negotiator ("I like North Korea with its Communist-style dictatorship ... but then I like South Korea with its democratic republic...") is inspired. Also right on the money is the impression of EastEnders' Pat Evans meeting Coronation Street's Ken Barlow in a motorway caff and BBC business editor Robert Peston's curious inflections as he presents a doom-laden weather forecast.

Jon Culshaw and Debra Stephenson interview

Now that they're back for another series of their Impressions Show, we gave Debra Stephenson and Jon Culshaw a ring to chat about the impersonating business, Eamonn Holmes's less-than-thrilled reaction to their send-up of him, and why Lady GaGa takes fashion advice from them...