Lemon chicken, a staple of a restaurant in London's Chinatown.[Photo by Mike Peters/ China Daily]

When in London for the Lunar New Year week, I met an old friend in Chinatown: lemon chicken.

If you are a foreigner in China, you are no doubt nodding your head. If you are a mainland Chinese, however, you may be scratching yours in confusion. Lemon chicken, you see, is a staple of Chinatown restaurants around the world.

I've never seen it in China, though, despite having lived in Beijing for almost seven years.

I'd known it well as a US college student, though I'd rarely craved the gooey stuff enough to make it myself.

I didn't know I'd missed it until this chance encounter in London. Suddenly, it sounded delicious.

A Chinese friend from Shanghai was traveling with me in London. When the dish arrived - crisp strips of deep-fried chicken in a tangy sweet-and-tart lemon glaze - he poked it with his chopsticks tentatively.

He took a bite and pronounced it good, but then shrugged: "Well, it's not Chinese food."

Our server, a young woman from Hainan, burst into giggles.

"Foreigners like it," she says, "but Chinese never eat it." Until she came to London, she adds, she'd never heard of it.

On New Year's Eve night, we'd strolled under Chinatown's red lanterns and feasted on more authentic fare amid the smells of roast duck and stir-fried home-style cooking. Lines were long all day - no reservations, sorry, first come is first served - and we finally sat down at Gourmet Kitchen to hong shao rou. The stewed fatty pork beloved by Mao Zedong, was the center of our meal, along with a mix of stir-fried greens (terrific), Shanghai-style soup dumplings (dry) and chicken fried rice (not sexy but flawless).

The next night, we went upscale, tempted by Mr Chow in Knightsbridge and a magnet for the glitterati in London, Beverly Hills and New York.

Low lighting, chic decor, and a glamorous crowd of international hipsters give the place a wonderful vibe. The menu leans to Cantonese with nods to Beijing, Shanghai and Sichuan. Like on many Chinese menus in the West, there is a romance with fermented black beans.

Seafood populates much of the menu at Mr Chow, and it's generally handled with brilliance: glazed prawns with walnuts retain a crisp edge under the light goo, while the fresh crabmeat soup was simple but very pleasant. Shanghai little dragon, those soup dumplings that disappointed us in Chinatown the night before, were spot-on here.

The disappointment came in the main, when we were encouraged to order the signature Ma Mignon, a tender and delicious tenderloin that's been a menu star here since 1975. We're not quite sure why: it's basically steak au poivre, with black pepper run amok and a sweet-spicy sauce that combined to mask the meat's obvious quality and less obvious flavor. (The by-the-glass Barolo, robust and elegant, paired so sweetly with the beef that it almost saved it. Almost.) We wished we'd stuck with our first choice, lamb with spring onion, or the drunken fish poached in wine sauce, which the Lebanese guys at the next table got that smelled so heavenly.

So what exactly was wrong with the Ma Mignon?

"Well," says my Shanghai friend, "it's not Chinese food."