[albertino]

My two cents
To put it simply, if somebody asks you, "Have you ever(=in your life) tried jellied eels?" without the time phrase "When you were living in London", then, a present perfect should be used. It conveys a sense of an "unfinished experience" from the past up to the moment you are asked.

However, if the time phrase element is added, then, the past tense should be used in the main clause, as the event "tried jellied eels" has been completed after you left for some other places or returned to your home country from London.

(a non-native-and-teacher helper)