Who will it be? Guess first and win a prize!

Rules:

• A guest will appear around 9pm. They will be called Mystery_Guest, so it is clear whose identity you're trying to guess.
• Ask them questions. Work out who they are. Enjoy picking their brain!
• If you make a guess at the guest's identity and are wrong, you are locked out from making another guess for five minutes. This is to stop you from making a hundred guesses every minute.
• The first person to guess correctly wins a signed copy of Buzan's Book of Mental World Records, more information about which is in the Olympiad section.
• The MSO staff's decisions are final and not subject to appeal. If you win, we will contact you for your name and postal address and may use it in our publicity.
• Have fun!

The mystery guest will be chatting live at http://www.msoworld.com/chat.html on Sunday 9th January between 9pm and 11pm GMT (US times: 1pm - 3pm Pacific, 4pm - 6pm Eastern). If you can't attend, we invite you to send your questions to us at chat@msoworld.com and look here after the event for a full log of the chat session - but if you don't attend, you can't win!