With difficulty!
I had a similar problem a few months ago, I managed to get the pin pulled out a certain amount and then I started bending it back and forth hoping the pin would snap, no such luck though.
I eventually used one of my kitchen knives that claim can cut through anything (a hammer head being used as an example!), and that's what did it in the end.
If you have one of those, then try that too, if not, could you nip into a local shop and ask them to do it for you?