Water Pistol wars come to London

Warnings abound about sparking a terror alert - see above link as water pistol game comes to London. Guardian article here
The official website says
StreetWars is a 3 week long, 24/7, watergun assassination tournament that has already taken place in New York City, Vancouver, Vienna, San Francisco, Los Angeles, and is now coming to London.
At the start of the game you will receive a manila envelope containing the following:
A picture of your intended target(s)
The home address of your intended target(s)
The work address of your intended target(s)
The name of your intended target(s)
Contact information of your intended target(s)
Upon receipt of these items, your (or your team's) mission is to find and kill (by way of water gun, water balloon or super soaker) your target(s).
You can hunt your target down any way you see fit; you can pose as a delivery person and jack them when they open the door, disguise yourself and take them out on the street, etc.
If you are successful in your assassination attempt, the person you killed will give you their envelope and the person they were supposed to kill becomes your new target. This continues until you work yourself through all the players and retrieve the envelope with your (or your team's) picture(s) and name(s). Then you win. Cash…but first live in fear.