Thanks.  I called the vet and he seemed to think it was quite amusing!
He said not to worry about it unless it keeps happening, and it's
been a few days now, he said it could be a furrball, but I've never
seen him with a furrball before.  So I'm just going to keep an eye on
him and if it happens in front of me I'll definately take him for a
check up.  I adore my cat but I sure wished I'd checked the insurance
policy small print before I took it out, he's costing me a small
fortune now that he's getting on in years, still he's worth it, bless
him.  By the way, the only thing the cat is jealous of is the
computer.  No matter where he is in the house, he seems to know when
I'm using the computer and miaows like crazy for attention and then
jumps between the monitor and the keyboard so I can't see what I'm
doing..