user: Question: Notes of BBC Radio 4, and a Director of Peter Kavanagh includes which average year?
Columns: ['Year', 'Title', 'Role', 'Director', 'Notes']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2002.0, 'The Angry Brigade', 'John Barker', 'Peter Kavanagh', 'BBC Radio 4']
SQL:

assistant: SELECT AVG("Year") FROM "Table" WHERE "Notes" = 'BBC Radio 4' AND "Director" = 'Peter Kavanagh';