ah fuck, I can't believe you've done this. 

A statement of frustration said when one is about to say something and is interrupted abruptly; usually with a punch to the face.

Note: It has to be said in a non-enthusiastic, brittish, calm and polite manner, if you will.

Example:

Some guy: "Hello everyone, i'm here today to talk about... *PUNCHED IN THE FACE*

Same guy: "Ah fuck, I can't believe you've done this."

ah fuck, I can't believe you've done this. by JoãoPaulo November 13, 2007

Ah fuck. I can't believe you've done this. 

Best response to being punched. Ever.

Guy #1: *Punches Guy #2 in the face*
Guy #2: "Ah fuck. I can't believe you've done this."

Ah fuck. I can't believe you've done this. by liMPiNMEdiC January 6, 2008

Ah Fuck I can't believe you've done this 

Expression of anger after someone has annoyed you

"Ah fuck I can't believe you've done this Barry why did you break my mum's lamp."

Ah Fuck I can't believe you've done this by Anti-hypofritz February 26, 2017