How odd, it's a different world from the private sector.
Not always. I have never told anybody (outside a business need) exactly what job I ever did since I left Uni. As for the Civil Service much of their work (whatever level) is with government protected information and a key way to protect information is not let anyone know where it might be found
Anyway it's something called the Civil Service Code and rules on contact with media. They also have really amazing (but sensible) rules on what happens if a civil servant runs for public office.