The Guardian have published an edited excerpt of Charlie's BAFTA/BFI Screenwriting lecture. Possibly there will be a YouTube video further down the track, but I'm only guessing. I particularly like Charlie's anecdote about a guy he used to see while jogging.

I run in my neighbourhood, and one day I ran past this guy running in the other direction: an older guy, a big hulky guy. He was struggling, huffing and puffing. I was going down a slight hill and he was coming up. So he passes me and he says: "Well, sure, it's all downhill that way." I loved that joke. We made a connection. So I had it in my head that this is a cool guy, and he's my friend now.

A few weeks later, I'm passing him again, and I'm thinking: "There's the guy that's cool." As we pass each other, he says: "Well, sure, it's all downhill that way." So I think: "Oh, OK. He's got a repertoire. I'm not that special. He's probably said it to other people, maybe he doesn't remember me ... but OK." I laughed, but this time my laugh was a little forced.

Then I pass him another time, and he says it again. And this time he's going downhill and I'm going uphill, so it doesn't even make sense. And I started to feel pain about this, because I'm embarrassed for him and I think maybe there's something wrong with him. And then it just keeps happening. I probably heard it seven or eight more times. I started to avoid him. (Source)