Home DIY

This is the kind of thing that a mitre saw (circular saw blade on an arm that you bring down onto the work-piece) is perfect for.

You get a straight cut every time, it's got enough grunt to go through the decking, and will in general make your life very easy - especially compared to doing it with a handsaw.

I was going to offer to lend you mine, but I'm South East London.

All of the above said, you can do it with a nice sharp handsaw, and they're significantly cheaper- buy a new one, they go blunt fast so don't dig an old one out of the shed.

The £90 one from B&Q online is a total bargain http://www.diy.com/nav/fix/power-tools/saws/mitre_saws/Performance-Power-210MM-Single-Bevel-Sliding-Mitre-Saw-10957626