Dr Martin Ellingham (Martin Clunes) welcomes in a tide of patients for his last day of surgery in Portwenn, in the final episode of this series of the comedy drama about a GP in a sleepy Cornish village. Before his move back to London, Martin dispatches a raft of last-minute medical cases, even tending to one of his removal men. Tasha (Sophie Thompson), too, is suffering a dizzy spell, and it remains to be seen whether Martin can make his departure without Louisa (Caroline Catz), pregnant, requiring his attentions.

So now everyone knows that Dr Ellingham is leaving Portwenn to take up a position at Imperial College in London. Louisa has overheard him talking about it and Pauline's steamed open the confidential letter offering him the position (and is upset about what it means for her), while PC Penhale learnt the news "on the street" (that would be that tiny road that runs in and out of Portwenn, would it?). Although a few of the villagers are sad to see the doctor go, the majority are much too busy smothering the pregnant Louisa with misplaced sympathy about how rotten Ellingham's been to pay his imminent departure much attention. Meanwhile, Bert organises a baby shower for Louisa, Joan turns her home into a B&B and the grumpy doctor really does seem to have overcome his aversion to the sight of blood.

Surely that can't be seaside doctor Martin Ellingham striding across Westminster Bridge? Yes, that's him, walking as usual like a man who's just got off a horse, heading for a crucial interview that could clinch him the surgeon's job at a posh hospital in the capital. It's a successful visit, though Martin lies about overcoming his blood phobia, but the journey home on the train is more eventful, when an expansive Portwenn drunk drops dead in front of him. There are nice scenes involving a philosophical train guard: "I suppose it reminds you how precious life is...to live each moment like the last, carpe diem, hakuna matata," but the drama barely dents Martin's breeze-block facade. It's hard to believe Martin wants to turn his back on Portwenn and its deranged inhabitants. Who'd want to leave irritating, clingy schoolteacher Louisa, even though she's pregnant with Martin's baby? And surely Martin could never turn his back on his daft aunt, who imprisons a horrible schoolchild in a chicken coop.

Still, this is a BBC Jane Austen and compared with Doc Martin, which last week beat it in the ratings, it is a masterpiece. Yesterday's episode, in which Martin Clunes waded through the usual shallow rock pool of West Country misunderstandings, was much weaker than the season opener, and continued to deprive us of decent scenes between the bad doctor and his pregnant ex, Louisa. There is gentle drama and there is soporific, and this seems on the turn.

Having succeeded Victor Meldrew as television's leading miseryguts in 2004, Dr Martin Ellingham (Martin Clunes) was well-positioned for a long and fruitful career, which he's continuing - begrudgingly - with this fourth series of ITV's popular pastoral sitcom, Doc Martin. In tonight's episode, the Doc bungles a consultation with an elderly couple, berates heavily-pregnant Louisa (Caroline Catz) for being too active, and toys with the idea of leaving it all behind for a high-powered job at Imperial College in London.

Terminally dense PC Penhale (John Marquez) provides most of the Cornish clot comedy tonight as rumour of a genetic illness in the family brings on a bout of hypochondria. Meanwhile, with even Doc Edith's (Lia Williams) flirting failing to loosen up our emotionally constipated medic (Martin Clunes), the romantic focus remains on ex-fiancée - but soon-to-be mother of his child - Louisa (Caroline Catz), who has prenatal anxiety.

Quickening of the pulse

"If we can keep it going imaginatively, without just trotting it out, I think it's worth it," Martin Clunes said recently about Doc Martin, now in its fourth series.

So much for cosy clotted cream Cornish whimsy, this was Doc Martin dishing out edgy philosophy laced with knife-edge drama. Well, it was for five minutes or so. The rest was jokes about blue wee and bisexual beardy blokes, but I have to admit that Doc Martin knows how to tweak my guilty-pleasure buds. It helps that each and every character in it is slightly potty, thus reinforcing the citydweller's view that the country/seaside is nice for a visit but you're likely to go a bit bonkers if you actually live there. It teases you too, keeping potentially intriguing characters such as PC Penhale and Pauline Lamb puttering around in the background when you want to dig deeper into their endearing lunacy. Indeed, there are times when Doc Martin would be better without Doc Martin, so the threatened departure of Martin Clunes could actually turn out to be a good thing. So what if its lobster pots are overflowing with cardboard cut-out eccentrics, there's just enough salt among the whimsical sugar to make Doc Martin perfect chill-out medicine.

In a battle between Martin Ellingham and Peter Kingdom over who had the superior sedately paced Sunday-night coastal-set drama, the harrumphing GP would win hands down. Martin Clunes's Portwenn doc, with all his suppressed yearning, is a fully rounded presence, something it's strangely hard to say about Stephen Fry's Norfolk-based solicitor. Tonight's developments are a case in point. At the end of last week's fourth-series opener, long-suffering Louisa turned up at Martin's place looking very pregnant indeed. And it's no time at all before she's dealing with doctor Edith, who - as we also gleaned from episode one - has something of a history with Louisa's former fiance. You'd never find all this on a show like Kingdom, where romantic angst seems to be restricted to the supporting characters. So it's very nice to have Doc Martin back in the schedules, quietly but appealingly going about its business with a central relationship that the writers consistently find interesting ways to refresh.

The pains of trying to conceive and Strangelove Syndrome are all in a day's work in rural Cornwall for Martin Clunes's Doc Martin. This second episode of the new series, however, is only really about his own relationship with Louisa (Caroline Catz).