Do you all have the "upper-decker" over there in the UK?

It's also known as the "backfloater". It isn't possible to inflict it on most public toilets because they're usually the type that just have pipework coming out of the wall to attach to the bowl. At least that's the case over here. For this stunt you need the kind of toilets people have in their homes or, say, in older hotels. It's the kind with the tank on the back of it with the heavy porcelain lid that you can lift off to jiggle with the valve or whatever. And by "whatever" of course, I mean "shit in it". This is a fantastic trick to play at house parties or wedding receptions or really wherever you can manage. It helps if you hate the people who own the toilet, though, or if they belong to the government, or they're your likewise degenerate drinking buddies. Step one, remove lid. Step two, shit in the tank. Step three replace lid. Step four, put on a nonchalant face and walk out. Step five, brag about it to your friends and instantly garner hero status for a month. The toilet's owners will be treated to a week of gradually lightening stinky cream-soda-tan water after each flush. Huzzah!