I plan to spend five days in a field of mud with 180,000 other middle class people in BMWs trying to look like they care about the planet.

In true hippy spirit you can reduce the total carbon impact of the festival by offsetting your CO2 output. I am a little skeptical about offsetting, from what I understand the idea is if I give even more of my money to the organizers at Glastonbury they will invest it in some green projects which in time will reduce the amount of CO2 chuffed into the atmosphere. So in a couple of years the planet won't know I've been to Glastonbury at all. Yippee!

So let’s look at a scenario, I part with 20 quid which they put in their bank account. A bit later on they will invest in a wind farm in darkest Somerset which everyone will hate. The wind farm will produce green energy and I will feel good that I have saved the planet in a small way. What troubles me is how do I know what they did with my money? Who’s to stop them claiming the wind farm was built with my money or with an EU grant? Also how do they know how much CO2 I'm going to produce? Surely that depends on what I do whilst I'm there?

For example my carbon footprint will be huge if I travel down in my friends 1970s' camper van doing 12 miles to the gallon, due to the added wind resistance of all the camping gear on the roof.

And if I spend my time smoking herbal cigarettes, sitting round a fire made solely of rubbish and polystyrene food containers and eat lentil curry, therefore massively increasing my methane output. How much CO2 is that, exactly?

I'm going to be much greener and do my own offsetting. I'm going to car share on the way down. I'm taking the wife. I'm not going to smoke (she wont let me). I'm not planning to burn anything. I will wear a kaftan to keep warm and I will not eat any lentils.

Most importantly I will wear a condom. If we don’t conceive while there our future carbon output by definition will be reduced by 50%!