Best rucksack for a 17" laptop?

FHKJ Posts: 151
edited October 2009 in Road buying advice
Sadly I have to cycle to work most days with my 17" laptop on my back. As I am adding a few miles on the way, I need a proper way of carrying it (together with a shirt/wallet etc). Currently I have a 'sling' style Incase backpack, but it slides everywhere and is driving me nuts!

Advice please, thanks, FJ