If MasterChef was about comedy instead of food, it's easy to imagine what John Torode and Gregg Wallace would make of this Ricky Gervais sitcom as it comes back for a second series.

"You've got tinkly piano music and genital warts," John would tell him. "Mate, those two things should never be on the same plate."

To which Gregg would add: "I'm getting the lovely light sweetness of Hannah and Derek, the sharpness of handyman Dougie played by Karl Pilkington, but then all I'm left with is this nasty, sour aftertaste in my mouth from Kev and that grubby pornographic gravy.

"There's a time and a place for sexual language like that and it just doesn't belong in a pudding."

I couldn't have put it better myself.

This week a new member of staff regales Derek with tales of strange creatures that are half-men, half-chimp, and Derek's father, Anthony (Tony Rohr) moves into the nursing home.

It's genuinely heart-warming to see him getting to know his son better.

Even if he is more interested in getting acquainted with all the female residents.

The pilot episode of Ricky Gervais's comedy set in a retirement home provoked a firestorm. The series that followed proved to be Marmite, so it's a surprise to find it back for a second outing. Critics protest that it mocks people with learning difficulties because Derek, the careworker of the title, shuffles around with his lower jaw stuck out and asks childlike questions. Naturally, Gervais - who also writes and directs - denied any such thing, arguing Derek can hold his own against Baldrick, Father Dougal and Mr Bean.

Like The Office, Derek is a mockumentary. The difference this time round is it's not obvious at whom we're supposed to be laughing. The result can be poignant, especially the scenes with Kerry Godliman, who is magnificently understated as put-upon manager Hannah - sometimes almost unbearably uncomfortable.

Tonight Derek's father moves in and is soon batting his eyelashes at the female residents, to his son's horror. Meanwhile, new member of staff Geoff bickers with the caretaker (Gervais's pal Karl Pilkington in ludicrous wig and gigantic NHS specs).

I can't get my head around Derek

A second series does give Gervais the chance to explore the characters more deeply, but with Karl Pilkington leaving in this opener the series instantly loses its main comedy draw.

Things we've learned in Derek Series 2 so far

Ricky Gervais and Karl Pilkington are back for the second series of Derek and we've already learned some pretty important lessons.

I don't know what happened to Ricky Gervais, but the grace he earned from The Office has finally run out. Derek is painfully unfunny and misguided in so many ways, but the most galling thing about this so-called comedy is how Gervais has convinced himself it's a significant, important and affective piece of social commentary. It's not. It's just lazy manipulation hiding its sins behind the fact it's ostensible about elderly care in modern Britain. But if that were true, why are the genuine old folks just silent stooges or background extras, as Gervais pulls faces next to grumpy best-mate Karl Pilkington in a comb-over wig? Abysmal. Even the title's font is bad.

Gervais shares his favourite clip from animated show

It may be hard to picture the usually unassuming Karl Pilkington as a ruthless boss who fires his employees with a single phone call - but that's where this little vignette from The Ricky Gervais Show comes in.

So sentimental is the final episode of Ricky Gervais's care home-set comedy that it's easy to think the whole thing is spoofing itself. The death of elderly resident Lizzie turns the team at Broad Hill introspective and we get their soundbite views on God and the meaning of life. Occasional moments of humour (mostly from Karl Pilkington's put-upon Dougie) are outweighed by cloying cod philosophising. To top it all, a maudlin reunion between Derek and his dad, an alcoholic, is sound-tracked by crashing chords from Coldplay. Channel 4, meanwhile, announced this week that there will be a second series.

Radio Times review

This week brought perhaps the worst episode of Derek yet. A young rapper called Deon (Doc Brown) came to Broad Hill care home to do community service, provoking the expected reaction from characters written by Ricky Gervais: awkwardness around a black man. Mentally vulnerable helper Derek (Gervais) touched Deon's hair and noted that it was curly, while crass drunk Kev (David Earl) tried to appear cool - "Blacks and whites unite!" - but then spoilt it by slagging off the "Chinkies".

Once Gervais had got that off his chest, Deon became a stooge in another sermon about kindness and respect for the aged. He'd turned up, unnerved and repulsed by having to interact with the elderly, just in time for a talent night at the home. Even naïve Derek would, if watching the show himself, have stood up after ten minutes and said: "Oh Christ, Deon's going to perform a heartfelt rap at the end about how he's changed his mind because the old folk and their carers are so inspiring, isn't he? Clearly he is. Yeech."

Derek would have been right. Deon also chipped in with a speech about how he'd realised that men in the home had fought in the Second World War, and that this trauma was more serious than the things he and his tough mates fight over. Meanwhile Derek confided to the show's unseen documentary-maker, ie directly to us, that he just wanted to make the residents happy, because they didn't have long left and every minute was precious. When Deon had done his rap, Derek said it was brilliant. Deon replied: "Nah. You're brilliant, bruv."

Jealous, snide critics are obsessed with Derek because they find its emotional manipulation so insultingly basic, they wonder how anyone ever concluded that it would work. Has Gervais lost it? Is he lost without Stephen Merchant? They also like to discuss what Derek tells us about Gervais's character: is the whole project an attempt to make us forget when Ricky spent ages unrepentantly using the word "mong" as an insult, because he's realised his apology came too late and his excuses didn't make sense? Tweets and interviews are combed for evidence of a superstar ego gone sour.

On the other hand, Derek's hardcore acolytes - it gets 1m viewers, which isn't great, but isn't as bad as many people hoped - think, in a nutshell, that because compassion is important and care homes should be invested in and celebrated, a show that says this is a good show. Whether the message is unbelievably heavy-handed or not doesn't matter.

Both camps will have looked forward to The Making of Derek (Wednesday C4; 4oD), which went out after this week's episode. It had self-serving scenes that were forgivable in a programme aimed at fans: at one point a series of supporting actors took turns to say how pleasant the show was to work on, and how nice Ricky is.

Gervais himself discussed the character of Derek. "He is kind and sweet and sincere," Gervais said. "So he's got to be scruffy, he's got to walk funny, he's got to have bad hair, he can't be that bright. Because then kindness comes along and trumps it all." Wait a sec. Why does Derek have to be like that? Isn't it a cheap Forrest Gump device to get away with simplistic, greetings-card sentiment, and make a "mong" the hero? No time to unpack that fully, as Gervais moved on to the show itself.

David Brent had a gulf between what he thought he was communicating and what he was really telling us, whereas everyone in Derek says exactly what they think. "That is the difference between this and traditional sitcoms - there's no level of irony, no juxtaposition [sic] between what people say and think and how we perceive them, which makes it sweeter and nicer and different."

Here is the essence of Derek. Gervais thinks he's refining the dramatist's art, not abandoning it, by making his characters bluntly state their agenda (and the show's) at all times. Yes, to most viewers it kills an emotional pay-off stone dead if you head straight there with no twists and turns along the way, but it's done like that intentionally.

It's almost as if Derek the programme is like Derek the character: completely guileless and hopeless at the task in hand, but well intentioned. The trouble is, it's a plea for sensitivity by a man with a long and ongoing record of insensitivity. Much of The Making of Derek was taken up with ribbing Karl Pilkington, who is actually the best thing about Derek by far but was now back to playing his character from An Idiot Abroad, ie an object of Gervais's laughing, vaguely bullying ridicule. The jarring sight of Gervais in fits at Pilkington suffering indignities on set, which meant Gervais was dressed as Derek at the time, summed up why Ricky's work will continue to fascinate us, even if it keeps sliding further and further into mush.

Lord knows Derek has its ups and downs, but however syrupy or preachy it gets, it's worth watching just for Karl Pilkington's turn as Dougie. The world-weary caretaker doesn't have a lot to do tonight, but one despairing speech he has is worth the price of admission on its own. Dougie is roped in to helping with a cabaret night, the centrepiece of which will be a performance of loutish Kevin's play about Duran Duran, apparently the only thing he cares about besides sex and Special Brew. Meanwhile, a would-be rapper is on community service at the home.

Ricky Gervais has courted controversy with his series about a retirement-home worker with learning difficulties. In tonight's episode Broadhill retirement home wants to host a cabaret show and Derek (Gervais) forms an entertainment committee to discuss plans for the evening. Meanwhile, a would-be rapper is on community service at the home. This is followed at 10.35pm by The Making of Derek, in which Gervais and his cast mates Karl Pilkington, Kerry Godliman and David Earl, explain why they made the series. At one point, Gervais becomes quite metaphysical about the whole thing: "The Office touched on existentialism but it touched on the existentialism of being 30. Derek touches on the existentialism of being 90."