The Donmar production of David Auburn's Proof (previews begin May 9, opens May 15, runs until June 15) may be technically sold-out thanks to having Gwyneth Paltrow as its star, but there are still ways of getting in.
As with any show, there will always be some returns on the day — these are sold at face value, for cash only, and are available (provided anyone returns tickets, of course) at the Donmar in person. Returns are limited to two per person.
The Donmar also operates a standing-place scheme. Fourteen standing tickets will be sold for each performance. Tickets are available in person only, from the Donmar box office, on the day, beginning at 10:30 AM. There are a maximum of two tickets per person, and this offer excludes May 9, May 15 and June 15.