Fans of Vietnamese food have for some time known all about Mien Tay, a fabulously good mini-chain of two restaurants. The first opened in Shoreditch – the prime UK destination for Vietnamese food – three years ago, and then in 2009 a second branch arrived in Battersea. That was good news for me because I live nearby and have become a regular. It's not just a good restaurant, but one that has kept improving: for instance, they went from having no wine list at all to having one specially put together by Willie Lebus of Bibendum, one of London's savviest wine merchants. Mien Tay now have a third branch, and it is time to bring tidings of comfort and joy to the people of Wellingborough, because that's where it is. (Apparently a fourth branch, somewhere in Fulham, is in the works.)

When I first saw the name of the new restaurant, Mien Tay Tu Dor, on a takeaway menu, I wondered what "tu dor" meant. Mien Tay, floating lotus petal of the Midlands? Mien Tay, third branch? It turns out to mean neither of those things because it's the English word Tudor. Doh! As soon as you see it, the Tudorness of the building is unmistakeable, and the not-unamazing fact is that it's older even than that: the lower ground floor wall dates from the 13th century, and the foundations were laid in about AD1,000. The dining room is a poem on the junction of Vietnamese culture, Tudor architecture and provincial English ethnic restaurants: bar at the far end, turquoise walls, statues, paintings and piped Vietnamese versions of western soft-rock.

My concern at writing about the out-of-town Mien Tay was that it would be less good than the London versions and I'd end up saying don't go here, go there. The outcome was more troubling still: this Mien Tay is better even than my local one. That might be to do with how quiet it was – on a Tuesday lunchtime, the two of us were the only customers in the place. We had the chef's full attention, and he made the most of it.

There is a starter that everyone who goes to any branch of Mien Tay has to try at least once: grilled quail with honey, garlic and spices. Even people such as myself who don't much like quail, and who find honey very easy to over-use, like this delicate but meaty dish, which comes with a dipping salt that both cuts and emphasises the sweetness of the honey. It's guaranteed to end with an obscene climax of finger-licking. Pork and prawn crispy pancake with bean sprouts is one of several Vietnamese dishes to which you add your own mix of lettuce, mint and dipping sauce. Fresh, crunchy and, thanks to the liberal use of green stuff that is such an attractive feature of Vietnamese cooking, light.

Of the several dozen times I've been to Mien Tay, this was the first time I didn't order a bowl of pho. That noodle soup, derived and upgraded from the French pot au feu, is one of the great glories of Asian cooking, but it is also astonishingly filling. (And very good value: a £6.30 pho with sliced beef and brisket for lunch, and you're not just full, you're immobilised.) I'm glad I didn't, because the other two courses were outstanding. A whole crispy sea bream came super-brittle on the outside, classically moist and tender in the middle, with a deep tomato and chilli sauce: just great. Minced beef was ground meat of high quality served with thrillingly delicate rice pancakes: if you don't lay them on your plate just right first time, they get irrecoverably twisted. This was another mix-and-dunk dish, with noodles, pickled carrots and cucumbers, herbs and dipping sauce. With a bottle of wine, all this came to £40 for two.

I hope they make a go of it here. They deserve to. It was a grim autumn day, and on the damp 15-minute trudge back to the train station we were pretty much the only sign of life, apart from a couple of blokes unloading supplies into a Polish deli. And yet there was my wife saying, "Lucky, lucky Wellingborough."

• Mien Tay 29-30 Sheep Street, Wellingborough, Northamptonshire, 01933 223031. Open all week, Mon-Sat, lunch noon-3pm, dinner 5-11pm (11.30pm Fri & Sat); Sun noon-11pm. Meal with drinks and service, from £10 lunch, £15 dinner.