You can walk around 99.9% of central London at any time of night and nobody is going to raise any eyebrows no matter how jet-lagged you look. But there's always

You can walk around 99.9% of central London at any time of night and nobody is going to raise any eyebrows no matter how jet-lagged you look. But there's always a chance you're going to attract some attention outside Parliament, or certain embassies, especially if there's an "elevated threat level" or whatever.