Below is the correct form of address for the Lord-Lieutenant:
In a letter: Dear Lord-Lieutenant
In a speech: Lord-Lieutenant
In a conversation: Lord-Lieutenant initially and then Mr Saunders Watson thereafter
The Lord-Lieutenant’s wife should be addressed as Mrs Saunders Watson . If the Lord-Lieutenant is represented by a Vice Lord-Lieutenant or Deputy Lieutenant at an event, they should be called ‘Vice Lord-Lieutenant’ or ‘Deputy Lieutenant’ initially.