You can after you have sold a property decide if you are going to treat that property as your main residence or another property you hold
Provided you do not attempt to treat 2 properites at the same tiem as a principal residence, you can make it your mind as you go.
As for the Mainwaring case unless you have access to documentation as to what was and was not declared and where the principal residence was claimed and where it was not
You are only speculating so now you are accusing him of being a tax cheat as well
REPORTED FACTS
the property the dispute is over was in Mainwarings name
