Thank you for this advice.
You say that my father could get back to a position of having a half share in the house. This would be great. Would that mean that, if the ownership of the house prior to the transfer was as joint tenants, he would be in a position to automatically inherit the other half share?
Does that still hold in the event of your first option "if your father did not know what he was signing he can contest the transfer on the basis of a lack of legal capacity to sign the transfer"?