Then I spent some time in London.

4 seconds sound clip from the Before Sunrise movie soundboard.

You can hear this line at 00:05:39 in the Blu-ray version of the movie.

Quote context

[...]

- How about you? Um... Mmm.

- Look, I was thinking about going to the lounge car sometime soon. Would you like to come with me?

- Yeah.

- Okay.

- So how do you speak such good English?

- I went to school for a summer in Los Angeles.

- It's fine here?

- Yeah, this is good.

- Then I spent some time in London.

- How do you speak such good English?

- Me? I'm American.

- You're American?

- Yeah.

- Are you sure?

- Yeah.

- No, I'm joking. I knew you were American. And of course, you don't speak any other language, right?

[...]