user: Question: What is the navy for Middleton with a home port of Portsmouth after 1983?
Columns: ['Navy', 'Name', 'Pennant', 'Commissioned', 'Home port']
Types: ['text', 'text', 'text', 'real', 'text']
Sample row: ['Royal Navy', 'Brecon', 'M29', 1980.0, 'HMS Raleigh']
SQL:

assistant: SELECT "Navy" FROM "Table" WHERE "Home port" = 'Portsmouth' AND "Commissioned" > 1983.0 AND "Name" = 'Middleton';