Life's Too Short/ Rev, BBC Two

Those of us who regarded The Office as a work of comic genius (not a word I use lightly) will, I'm afraid, take some convincing about Stephen Merchant and Ricky Gervais's latest offering. Keen fans who have followed the duo's every move since that landmark sitcom will feel they know every last trope on display in Life's Too Short, from its mockumentary setting and unPC subject matter to dark comedy and celebrity guest spots.

All those and more are present in the spoof documentary written and directed by Merchant and Gervais, in which they also appear. It's about Warwick Davis (played by Warwick Davis himself, of course, another Merchant/Gervais touch of an actor playing a ghastly magnified version of themselves), a washed-up star whose marriage is on the rocks. He happens to be a dwarf - a description, by the way, that Davis has said in interviews he is happy to be used, along with the term little person. The sitcom, which debuted last night in a seven-part series, continues in the postmodern, self-referencing and deeply ironic trend that Gervais and Merchant started with The Office and continued in Extras and The Ricky Gervais Show.

It's certainly funny in parts and Davis (who was in Star Wars: Return of the Jedi and Willow, and appeared in Extras) shows himself to be an actor with great comic timing and – crucially in a comedy of this kind – one of notable subtlety. There are lots of asides to camera and much humour to be gained from his lack of height, but these scenes are played with an assured lightness of touch.

Davis the character is an entrepreneur who runs an agency called Dwarves For Hire, and in his sharp suits and four-by-four fancies himself as “a sophisticated dwarf about town” whose groundbreaking work for a minority bares comparison with the efforts of Martin Luther King. But he is no hero. His wife hates him and the only work he offers his talent is in panto, even if they don't aspire to it: “You're a dwarf – how can you not know 'Hi Di Ho'?” he asks one.

Life's Too Short, on this evidence, is disappointingly predictable and therefore appears lazy, but sitcoms should never be judged solely on their opening episodes

With his lack of self-awareness, vaulting ambition and belief that everything that falls from his mouth is a golden nugget of insight and wit, Davis is another David Brent (in fact, one could almost hear Gervais saying Warwick's entire script himself), and Shaun Williamson, who also appeared in Extras, is playing exactly the same character here – a desperate out-of-work actor being humiliated by the programme-makers – while Davis's useless accountant is merely another version of the incompetent agent that Merchant played in Extras. In treading previously well-excavated territory, Merchant and Gervais are almost certainly playing a private joke here, but I'm not sure how many people will be amused by it.

It was only when Liam Neeson made an appearance five minutes before the end that the first episode came to life, as he breezed into Merchant and Gervais's office to ask for their help in making him into a stand-up comedian. His cameo was predictably that of a celebrity willing to send himself up – he got the lead role in Schindler's List because, he said, he makes lists all the time – and he barely noticed Davis sitting beside him because to a big Hollywood star like him (or rather, to the fictional Liam Neeson) he's a little person in both the literal and metaphorical sense. Further celebrity cameos, by Les Dennis, Johnny Depp and Sandra Bullock, among others, follow later in the series.

Life's Too Short, on this evidence, is disappointingly predictable and therefore appears lazy, but sitcoms should never be judged solely on their opening episodes. Merchant and Gervais have deservedly won bucketloads of awards for their previous work, which has – honourably – never played to the gallery. For that reason, I'll stick with the show in the hope that it enters new territory over the coming weeks.

Rev, which has returned on BBC Two for a very welcome second series, should certainly not have been judged on its opening episode last time round, for it was a slow burner that moved at a gentle pace and had few laugh-out-loud moments until we got to know and love its characters. But it was worth persevering with as we got to know Adam Smallbone, a vicar whose faith is constantly questioned by the vicissitudes of running a challenging inner-city parish with a tiny congregation. Not to mention by a lawyer wife (Olivia Colman) who doesn't entirely share his beliefs and who resents the time he spends with his flock rather than making babies with her.

Last night's episode opened with Adam (played by Tom Hollander [pictured above], who created the series with James Wood) at a retreat where his conversation with God was interrupted by thoughts about lunch – he hoped it wouldn't be “that strange cauliflower cheese again” – and Hugh Bonneville's bumptious and urbane Roland, a fellow student from theological college days, who would really rather be on retreat in France. But word had got out and so it was full, “the bastards”.

Adam became an accidental hero when a mugger bumped into him in the street, dropping the handbag he had just stolen from a parishioner. She thought Adam had wrestled the thief to the ground and nominated him for an award and he, tempted by the sin of vainglory, allowed himself the adulation.

There is so much to enjoy about Rev – a witty script, an excellent cast (which includes Miles Jupp as a lay reader and Simon McBurney as the Archdeacon) and believable storylines – but what most impresses is that it dares to address matters of faith among the comedy. Last night Ralph Fiennes delivered a cameo as “the Bishop of London”, a father-confessor figure who winkled out the truth from Adam about his pretend heroics and gently guided him to doing the right thing. It was a deeply poignant scene about having a conscience and how it often makes life harder for those in possession of one.

But I mustn't misrepresent what is often a very funny half-hour with some broad comedy, even if last night’s best scene was a subtle theatrical in-joke. The bane of Adam's life – the rather ungodly but politically astute Archdeacon (played with relish by McBurney, co-founder of theatre company Complicite) – said when he had to rush off from a meeting: “I've got tickets to watch David Hare read some of his emails at the National.” Blessed be.