Free Roam Mode Successfully complete all standard missions to unlock the "Free Roam" option.
Kelvin Deamer Mode Successfully complete the game to unlock free roaming mode. Then, go to the golf cart that you will find in one of the parks. Press Up, Down, Triangle, Down, Triangle, Left, Right, Circle, to be transformed into a character known as Kelvin Deamer.
Skip Intermission Sequences Press R3 to skip some intermission sequences. Note: Not all sequences can be skipped.
Health Recovery If you have been getting damaged by enemies and are close to dying, walk up next to a wall. Your character will lean up against it in order to recover. With each breath your character takes, part of his bullet holes disappear until he is fully recovered. This may take a minute - make sure that no enemies are attacking you.
Hidden Vehicles You can find some hidden vehicles in the parks of London, such as a Sooty Van and a golf cart parked behind huts and bushes around the parks. To get the Concept Lexus and a Triad Gang Car in Free Roam mode, in the mission where Carter infiltrates Jolson's warehouse, go to Chinatown (located in Soho). Go down into the underground garage. The position of the cars varies on each floor.
Indicators In free roam mode, for added realism you can use your indicators (turn signals). Press L1 to indicate right and L2 to indicate left.
Gas Cylinder Kills Shoot a gas tank when an enemy is nearby to easily kill them.
DC Carter Knock out hostage: With a gun, press X to get a hostage then press Square. Kick hostage: While unarmed, X to get a hostage then press Square.
Mark Hammond Shoot hostage: With a gun, press X to get a hostage, then press Square. Break hostage's neck: While unarmed, press X to get a hostage, then press Square.