Sardo Canale, London, NW1

One of the hazards of being a restaurant reviewer (OK, the only hazard) is that your judgements can hang around long after they have lost their relevance. It is not unusual for an ancient review to still be plastered on a restaurant's window, years after its sentiments were pertinent. Occasionally, I get out a black marker and scribble: "I meant it then, but that was before three changes of chef, the new all-you-can-eat policy and that problem they had with the dogmeat in the freezer," but otherwise, you just have to live with it.

One of the hazards of being a restaurant reviewer (OK, the only hazard) is that your judgements can hang around long after they have lost their relevance. It is not unusual for an ancient review to still be plastered on a restaurant's window, years after its sentiments were pertinent. Occasionally, I get out a black marker and scribble: "I meant it then, but that was before three changes of chef, the new all-you-can-eat policy and that problem they had with the dogmeat in the freezer," but otherwise, you just have to live with it.

So the website of Sardo in London's Fitzrovia carries an excerpt of a review I wrote in 2001 in which I said: "Sardo is great. Sardo is beautiful. Sardo is the sort of place you could happily go back to once a week for the rest of your life."

True to my word, I did keep going back, taking friends from New York, Sydney, Hoxton. But the love affair ran its course. Federica the Beautiful moved on, the food lost its thrill, and the service became ordinary. Even I had to admit the magic was gone.

But was it me or was it them? The best way to answer that question is to visit Sardo's new sibling, located in a yuppie-scum converted warehouse beside the Regent's Canal. Owners Romolo Mudu and his elegant daughter Bianca preside over an impressive space, thoughtfully divided into several separate dining areas, including a bar/lounge in what was once a cobblestoned barge-horse tunnel. Slate floors, bare wooden tables, and a swish stone bar all add to its sleek charm, only slightly diminished by the loud crowd of locals sporting creased linen and sensible shoes.

With its own kitchen herb garden, and sunny courtyard complete with a gnarled 300-year-old Sardinian olive tree, it feels like a self-contained Mediterranean island in Primrose Hill, if you could have an island in a hill.

The menu bears more than a passing resemblance to its Fitzrovia counterpart, with a mix of Italy's greatest hits (carpaccio of beef, linguine with crab, veal escalope) and traditional Sardinian dishes such as malloreddus pasta with tomato and sausage, fregola (small couscous-like pellets of ground semolina) with prawns, mussels and courgette, and an antipasto platter of cured and sun-dried tuna, marinated anchovies and swordfish.

A selection of local meats and cheeses (£15 for two), served on a wooden plank the shape of a bent cricket bat, is a neat introduction to the flavours of this mountainous Mediterranean island. There are furls of wonderfully nutty prosciutto; soft and sweet, thinly sliced coppa (cured pork shoulder or neck), and slashes of dense, tough, big-flavoured Sardinian salami. Also present are three variations on pecorino cheese - fresh, aged and a fierce and feral crema di pecorino piped on to shards of excellent Sardinian carta di musica crispbread.

The wine list wanders all over Italy, and it is the Sardinians that send out the siren call, from a beautifully light and crisp white - Vermentino di Gallura by Piero Mancini ( £19) - and a rich, full, silky red, Nabui Monica di Sardegna from Cantina Nuraghe di Mogoro (£31).

Branzino al profumo di limone e rosmarino (or sea bass with a sweet and sour sauce) served with fregola (£16.50) could not sound more enticing. The ancient use of agro dolce (bitter/sweet) flavours, done well, can be mesmerisingly good, but this is just a mess, the lightly sautéed, good fleshy fillet of skin-on sea bass let down by a sticky, sweet sauce. Even the fregola has given up, and feels dry and lifeless. There is a gap, it seems, between the promise of the menu, and the reality offered by the kitchen.

A big dish of linguine with crab (£10.90) is just at that right, tough side of al dente that Italians seem to achieve without really trying, but the crab is playing "Where's Wally?", adding no real sweetness or flavour. Having cooked tagliolini al granchio myself the night before, and wallowed in its sea-sweet crabness, this is a third cousin, twice removed.

Desserts seem to be French-inspired with Italian subtitles. Meringata ai frutti di bosca con sorbetto limone (£5) is baked meringue with strawberries topped with a scoop of lemon sorbet and a tuile biscuit. It's too fancy, too sweet, and not very well made, with crunchy, undissolved sugar crystals in the meringue.

Zupetta di pesche (£5) is a tangy peach compote, topped with a scoop of berry sorbet encased in a kind of sugar cage. For heaven's sake, now I'm getting annoyed. The spun toffee isn't the problem in itself, but I sieze on it as symptomatic of the changes I have witnessed since my original review. More time is now being spent on looking good than on being good.

So Sardo isn't great any more, but it isn't bad either. It's just OK. The new place has a nice vibe, good, professional staff and a real sense of energy. The Sardinian crispbread (pane carasau, or carta di musica) is still a knockout, and the canalside location (though the canal is not visible) has enough charm to be filled from noon to night with the locals for evermore.

I still think the magic has gone, but I'll be happy to eat my words again in another three years.

13 Sardo Canale 42 Gloucester Avenue, London NW1, tel: 020 7722 2800. Open Tuesday to Saturday for lunch and dinner. Around £85 for two including wine and service

Scores 1-9 stay home and cook 10-11 needs help 12 ok 13 pleasant enough 14 good 15 very good 16 capable of greatness 17 special, can't wait to go back 18 highly honourable 19 unique and memorable 20 as good as it gets

Second helpings: More canalside dining

Bruerne's Lock 5 The Canalside, Stoke Bruerne, Northamptonshire, tel: 01604 863 654 Situated alongside the Grand Union Hotel, this red-brick Georgian building has been a general store, a post office and a surgery. Today, it continues to contribute to the welfare of the community of Stoke Bruerne as the village's most popular restaurant and function venue. The dining-room is formal yet comfortable and the food runs from pesto chicken with polenta to spiced Moroccan lamb.

Denial 120 Wharfside Street, Birmingham, tel: 0121 632 1232 With its prime canalside location at Birmingham's Mailbox shopping centre, buzzy bar scene, and modern British cooking, it looks as if Denial has been able to transcend the silliness of its name. Sit on the outside terrace on a sunny day, or bag a romantic canalside table in the dining-room for dinner.

Simply Heathcotes Canal Wharf, Water Lane, Leeds, tel: 0113 244 6611 This converted Grade II-listed warehouse combines a nice modern feel, good water views and the now patented Paul Heathcote mix of modern British cooking and classic comfort food. Start with grilled fillet of smoked mackerel, move on to honey-glazed Goosnargh duck breast and finish on good old bread and butter pud or knickerbocker glory.

E-mail Terry Durack about where you've eaten lately at t.durack@independent.co.uk