The Host City Contract for the London 2012 Olympics.

This is the non-negotiable contract document prepared by the IOC to be signed by whoever won the bid at Singapore in 2005.

There are a number of detailed technical manuals that form an integral part of the contract but are being kept secret at the request of the IOC.
The Technical Manuals have now been released by the Greater London Authority after intervention by the Information Commissioner and are available here