Love Actually (2003)

Continuity mistake: After Sarah has called at Harry's office, Harry prepares to open his office door to see her out. The camera cuts back to Sarah for a moment, then back to the camera angle on Harry as she walks to the door. In that short space of time, the sliding cupboard doors have changed their configuration, and the blinds in the upper left of the frame have partially closed. (00:18:45)

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Harry: Tell me, exactly, how long it is that you've been working here?
Sarah: Two years, seven months, three days and, I suppose, what, two hours?
Harry: And how long have you been in love with Karl, our enigmatic chief designer?
Sarah: Ahm, two years, seven months, three days and, I suppose, an hour and thirty minutes.
Harry: I thought as much.
Sarah: Do you think everybody knows?
Harry: Yes.
Sarah: Do you think Karl knows?
Harry: Yes.
Sarah: Oh that is bad news.
Harry: Well I just thought maybe the time had come to do something about it.
Sarah: Like what?
Harry: Invite him out for a drink and then after about twenty minutes casually drop into the conversation the fact that you'd like to marry him and have lots of sex and babies.

Trivia: Billy Bob Thornton agreed to appear in the movie without having seen the script. On the day of shooting he told director Richard Curtis that he was scared of Benjamin Disraeli's facial hair, and as such wouldn't be able to do the scene in Ten Downing Street because there was a picture of him on the wall. Curtis told him to keep his back to the picture throughout the scene, which he does, although you'll notice he looks quite nervous.

Question: Even if Karl and Sarah don't get together at the end, I couldn't see what exactly was stopping them?