I can probably count on one hand the number of public restaurants in London that still require a tie at dinner. Nevertheless, I prefer to dress up a bit when I go out, and not wearing a tie seems a shame. Instead, I find that a relatively casual dinner with friends, when a tie isn't really required, is a good chance to wear something a bit more unusual.
This particular one was given to me by my father and is a really lovely loose knitted woolen tie in dark red (it looks a bit orange here, but that's poor photo quality I'm afraid). It's too casual for many occasions, although it does look great with a plain grey suit, but I find it's perfectly suited to wearing out to dinner with this rather worn black blazer for an effect that's reminiscent of evening wear, but still firmly at the 'casual' end of 'smart-casual'.