Yes, it was London, near Southgate. I must say, though, that overall most of the British people I've met in my travels there were polite, patient and helpful, especially in the North (Liverpool, Manchester, Southport). I must also particularly mention the folks in Inverness, Scotland - some of the friendliest people I've ever met!
I've also met some very nice and friendly Londoners, too. I remember on one occasion I was traveling alone and had a rental car (I hadn't meant to drive all the way into the city; I'd planned to find a hotel in Hatton Cross or somewhere on the outskirts and then just park the car and take the Tube into town. But I got caught up in traffic on the motorway and before I knew it I was passing the Houses of Parliament and Madame Tussaud's Wax Museum.) Anyway, I literally drove in various circles for over two hours, trying to negotiate traffic while driving on the "wrong" side of the road *and* find someplace to park so I could ask for directions. I finally ended up back on a motorway and pulled off at the first "Services" area. Inside the gas station I must've looked borderline hysterical, because one clerk kept offering me a cup of tea, insisting it was "on the house." Another customer, an older man, was trying to give me directions to a Traveler's Lodge: "Just go right straight through the next roundabout..." (Do I go right? Or straight?) "....nip up the Wickershams, rally 'round the gorm and scumble and Bob's your uncle, you're there!" (Who's Bob?)
Anyway, sorry for the novel but I did want to report that I don't lump all Left Ponders in with that rude fellow I encountered. :-D