Thank you all for your input.
For my part, if Ryanair want to enforce the rule then OK. I don't have to fly with them again. I probably won't now in any case since I do not wish to place myself in such an embarassing situation again.
The real point is that on 5 (not one but five!) previous occasions flying the same route and carrying exactly the same configuration of baggage (i.e Briefcase, Laptop and one small Hold piece) it was perfectly acceptable for me to take the laptop and my briefcase into the cabin.
Inconsistency breeds confusion and anger. ALL check-in staff should be working to the same set of rules and Ryanair should clarify the ruling with a definition of a handbag, be it for a lady or a businessman and it's relationship to a piece designated as carry-on baggage.