There are two answers to this:
1. It depends where you're flying. If you're an EU citizen within the EU, then you don't need a passport to travel, just "suitable identification". The practical problem is that for Brits with (as yet) no government issue ID card it can be hard to persuade customs etc that you have anything they regard as suitable.
2. It depends how long ago you were told this. My first CPL had a photograph on it and a paragraph stating that it had the privileges of a passport. You then didn't in theory need to carry a passport, but in practice had the same problem as above. The Home Office removed this privilege some decades ago now, so the CAA removed the requirement to have a photo on your licence just in time for all sorts of security stuff to bring in the requirement to always have photo ID. Great!
