Mystery play’s a sellout

Talk about box office drawing power.

The play doesn’t open until Sept. 8. No one knows what it’s about. There isn’t even a title.

Yet all 16,000 tickets available for advance sale at London’s National Theatre have been sold, Britain’s Guardian newspaper reports.

What’s the draw? Writer-director Mike Leigh. It’s his first play in 12 years after turning out such films as “Vera Drake,” “Topsy-Turvy” and “Secrets & Lies.”

To enforce the secrecy, rehearsals aren’t even being held at the National.