So how exactly does a transfer window extension work?

Despite my headache and the fact it's after 11pm in London, the transfer window stretches on for Arsenal. The deal for Danny Welbeck wasn't completed by the time the window closed, but that doesn't mean the deal won't happen. Arsenal and Manchester United have submitted a "deal sheet" to the Premier League, meaning they get an extension to complete the details of the deal.

What's that, you ask?

So, in other words, we have two more hours (well, closer to one and a half, now) before the deal has to be totally and officially completed. If both clubs and the player are acting in good faith, it should essentially be done at this point, and the completion of the deal should be a formality. But I think we all know better, and this headache is absolutely not going to go away until after I see "Danny Welbeck" in an official Arsenal tweet, or something like that.