Safe ways of Posting?

[Declan]

So, I have my guitar, and somebody is up for a trade. Thing is, I'm in Oldham Manchester, and they're in London. I would take the coach down, but it'd take faaar too long, and have uneeded expenses, particularly just for a Guitar.

What are the options with post? Is there a way either one of us could post off our guitar, and the other one is made to keep their end of the deal up? If not, I'm really sceptical about posting off my guitar, unless they did it first...If this guy is honest, he'd probably be thinking the same thing...