Over time he gradually became more tame again but I wasn't confident at all that we'd be able to catch hold of him and put him in a cat box. In the end I borrowed a 'cat-trap' from a lady in Portmagee who runs an animal rescue/rehoming service.
I was really heartened by how willingly he went in this far (though if you look in the photo, he's ready to run if he has to!) - the next day I held my breath and put the food right at the back of the trap and crossed my fingers.....and it worked!
I'd the vet on stand-by in town and they were able to operate on him straight away -- I went off to do a bit of shopping and then came back about half an hour later and it was all done.
He wasn't very happy at all: I think being caught in the trap was very stressful for him, and then having his operation on top of it all. I was worried that he was going to run off and not come back, but even if he did at least I knew that he'd been neutered now so he wouldn't spend his days tom-catting around and fighting.
BUT...he's like a different cat now that his hormone levels have flattened out a bit. The other cats are very wary of him; I think his size intimidates them all but they just give him a wide berth and generally things are ok. Bertie is the most vocal opponent to this new addition but they just avoid each other as much as they can.