Another answer on SE Aviation (Why pilots would leave the cockpit in a short flight? ) had this bit of information in it:
The cockpit of some airliners lacks a lavatory.
Isn't is more the other way around: i.e. A Lavatory inside a cockpit is a rarity?
Which airliner cockpits have an entire Lavatory inside them?
I always thought the Flight Crew came out to use the forward-most Business / First class lavatory.