user: Question: What is Date, when Opposing Teams is "Australia", and when Venue is "Twickenham , London"?
Columns: ['Opposing Teams', 'Against', 'Date', 'Venue', 'Status']
Types: ['text', 'real', 'text', 'text', 'text']
Sample row: ['Wales', 6.0, '19/01/1991', 'Cardiff Arms Park , Cardiff', 'Five Nations']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Opposing Teams" = 'Australia' AND "Venue" = 'Twickenham , London';