There's a one-off Ricky Gervais comedy-drama on Channel 4 tonight called Derek (10pm).

It's a bit of a departure from Gervais' normal stuff, the main character being a simple but honest guy who works in an old people's home (alongside his pal Dougie, played by Karl Pilkington, who I have to say doesn't seem to be acting much).

It's hard to imagine this one would have got commissioned without the involvement of Ricky Gervais.

He writes, directs and stars in this one-off comedy drama about a simple soul called Derek who works in an old people's home.

His mate Karl Pilkington is in it too (as Dougie), in what is easily the worst hairpiece in TV history.

There are occasional smiles, but this doesn't have the savagery of Getting On, the BBC comedy on how we treat the elderly.

This is a much more sincere, poignant little piece and although Derek and his co-worker Hannah (Kerry Godliman) love their jobs, the fact remains that most people have a horror of ending up in a place like this - even if it is only on the telly.

Ricky Gervais follows up Life's Too Short with a show about a simple, vulnerable man working in an old people's home. Brave, but this isn't the moment where Gervais is consumed by political incorrectness once and for all: Derek is nearly a brilliant reinvention.

You'd have to try hard to read Gervais's portrayal of slow, sweet Derek as mockery, and the sad ending is up there with David Brent's "Don't make me redundant" meltdown. Kerry Godliman shines in a supporting role as Hannah, the care worker who is Derek's best friend and is thwarted, selfless, burningly sad but endlessly compassionate - every moment she is on screen is sigh-inducing magic.

But Derek falters because Gervais, who writes and directs without Stephen Merchant, is too reliant on tropes from his previous work. The action is shot as a documentary about the characters, a device that doesn't add much and highlights the occasional, inappropriate similarity between Derek and Gervais's other creations. Casting Karl Pilkington as another of Derek's colleagues also breaks the spell, and sometimes the mix of slapstick and sensitive drama is uncomfortable.

Despite some brilliant cameos from Liam Neeson and Johnny Depp, we're thrilled to see Ricky Gervais leave Life's Too Short behind and return to the workplace sitcom. Gervais' new Channel 4 special is set in a retirement home and features the acting debut of An Idiot Abroad presenter Karl Pilkington as Dougie the caretaker. While some (particularly fellow comic Stewart Lee in the Guardian) have pre-emptively damned Derek as insulting, others are praising the script and calling for a full series - all we know is that we can guarantee #derek will be trending on twitter tonight...

Derek represents something of a trap for critics hoping to hammer home the idea of Ricky Gervais-as-heartless-bastard. Carrying out an unspecified role in a provincial care home, Derek's an eccentric. Indeed, with his permanent gurn, inadvertent gift for physical mishap and general air of bewilderment, some might assume that he's in some way disabled and draw the obvious conclusions about his creator's motives. Gervais says not. Instead, Derek is marginal. He bonds with the old folk, indulges in nonsensical conversations with caretaker Dougie (a debut role for Karl Pilkington) and imagines himself as a possible suitor to the home's manager Hannah, who, while lonely and unfulfilled, is way out of his league.

Derek is hard to judge on the basis of a pilot. Some of the comedy is incredibly broad. Derek sits on a pie. Derek falls in a pond. We're laughing at him, but, before long, we're sympathising too. A couple of scenes hint at the show's potential tenderness and tragedy and suggest that a series - which Gervais is already writing, without frequent partner Stephen Merchant - would be worthwhile.

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Creator of Channel 4's one-off show Derek also condemns horse-racing two days before the Grand National.

So I suppose we'd better get Derek (Channel 4), Ricky Gervais's little (comedy?) drama set in an old peeps' home, out of the way first. To begin with, I can't see what all the fuss is about. OK, so the title character isn't the sharpest tool in the shed, but is that really mocking disabled and mentally ill people? Can you ban simpletons, even ones who are bathed in a warm light? Baldrick, Bean, Bottom, all cancelled, by PC plod?

I think the columnists and critics who have been sharpening their pencils to stick into Ricky's eyes are doing so because of previous lapses in judgment. I mean Mong-gate of course. But Derek isn't controversial.

Trouble is, nor is it very good. The whole mockumentary thing feels tired now (and what are these films being made, do you ever wonder that?). There's a lack of confidence about it too. The humour (if you can call it that) yo-yos between standard been-there Gervais Office squirmy awkwardness and sit-in-a-custard-pie/fall-in-the-pond slapstick.

Most of all, though, I'm not feeling the character - I'm neither moved nor amused by him. In The Office and Extras, Gervais was basically playing himself. He was someone you could loathe and love at the same time; you could begin to understand how it would feel to be him. Derek, a much more sympathetic character, is someone else, and so requires more acting. Which, perhaps, given this awkward show of haminess, isn't his forte. Neither is it Karl Pilkington's, as Derek's sort-of mate - not much hope of best supporting Bafta, I'd say, though he's probably straying less far from his real self.

Its a shame. I really wanted it to be good. To shut up the Gervais bashers, for one, who may even be more annoying than Gervais himself. But also - and mainly - because he used to be so good. Remember?

Ricky Gervais in Derek, Channel 4, review

In Derek, Gervais seems to have found a character that he relates to deeply.

James Cary: Derek review

Overall we have a comic problem. In a comedy, lead characters need to have flaws on their character and clear quests. Derek has flaws, and they're not his fault, and so comedically it's hard to generate comedy stories, scenes and moments.

Derek review: No Ricky Horror Show

But Gervais has undoubtedly opened the flood gates here. By writing, directing and starring in the show - he has once again aligned himself to a potentially inflammatory perspective on the less abled amongst us.