After posting that telling you to try it, I forgot to come back and mention you need to be very careful!
If it's really tight, it can tear the filter, then you're potentially a bit screwed.
We almost messed up on Freeman's filter. Stuck an allen key through the hole in the bolt (K&N filter), then hammered on the end of a flat head screwdriver against the allen key. A couple of hits and it tore half the head of the filter off. Didn't realise how weak they are.
Yeah I had this with the CBR. Eventually got it off by crushing the end with some grips and carefully turning