Not once in your lifetime ever trust Dave. Untrustworthy bastards I say

I'm a furry. :P

when I was at uni, there is this prank program, the icon is cola, so it looks very innocent and like a game, but when you double click to launch it, it makes your computer screen goes like police car siren, red, and blue, and screen will say, stop looking up ****, xxx, and stuff like that, if the speaker is on, the siren can be heard too. ideal for open plan office. so have a go and find it on google but send it to the bugger using a good and reliable middle man, if you time it right, wait til some big ceo/management or hr is around his desk, launch it, awesomeness

Ehm, as a specialist in that area (but in a different country, not sure what the law is in the UK), I can tell you it is actually illegal for the employer to be spying on employees, unless he has a really valid reason you know? This is something most people don't know, but unless the employer has a valid reason for doing this, it is highly illegal to be spying on employees. Even in the workplace, you have the basic right of privacy! And, as far as I know, this isn't any different in the UK, but the specifics may differ...

Find out where he lives and paintball his house. If that does not work, burn it down. All in fun, right?

YDI. If you lend sb your computer you should log off and they should log in using their account. That way he would be the one visible as the person wathing ****, even from your computer...

Deep-freeze a can of shaving cream for several days, open the bottom, then put it in his desk. When it heats up, all the foam will overflow his desk.

Laxatives and Viagra in his coffee, that is all

bake him some cookies. some green, hard hitting, put-you-on-your-ass cookies right before a big meeting. I did it to my chem teacher before class:)

Eye drops in his drink