Is That A Compliment?

For the second time, yesterday morning, my boss's boss, impressed with my solution to a problem said...

That John has a head on him like a bastard cat.

Now I know from checking after the first time that this is a compliment, but being an insecure sort it is a compliment that triggers the thought that it is an insult. If anybody has heard this before could you please tell me what the origin is?