One of the best things about regularly attending festivals is that you can build up a real panoply of prize-winning, cut-and-keep anecdotes about truly awful times you've had. In the absence of this nation going to war, festivals provide the only chance most of us will have to catch trenchfoot, stand in a queue for a dwindling supply of blankets, be helicoptered out of a flooded wasteland with a broken leg, or simply wander around at 4am, staring into people's faces and screaming “Why?”

Eighty per cent of your festival experience is simply and unalterably down to the weather and, as many of you may have noticed - perhaps bitterly, covered in mud, while waiting for Oasis - the past few British summers have been quite rough. But there's a reason why that “Keep Calm and Carry On” poster is such a hit - and you find its living embodiment at a British festival, the night after a cataclysmic thunderstorm. Everyone comes out of their tents, sighs, puts on their wellies, puts a tot of whisky in their tea at 9am, lights a fag and gets on with it.

Wellies and whisky are pretty much the other 20 per cent of a “good” festival. You must take boots to a festival. I cannot say “must” enough. Must must must. Must. No matter how balmy and Moroccan the weather forecast, boots boots boots. The BBC's online weather forecasting service is particularly betrayment-prone - its cheery certainty about Glastonbury 2007 is why my husband spent the festival with two mud-clagged bin-bags wrapped round his legs, saying “But the BBC said it was going to be sunny!” every 20 minutes. Of course, my husband still looked quite prepared by comparison - every festival has a small, sad, coat-less crew of 14-year-old scallies in white, box-fresh trainers and hoodies, standing under a tree in the pissing rain, trying to work out how they can get to the Klaxons without actually drowning.

The whisky doesn't have to be whisky. Anything that allows you to take “tots” in tea or coffee will do. This reliance on spirits is a matter of simple logic: drink voluminous alcohols, such as beer, and your toilet needs will double. When cider was my tipple, I would be toileting once every hour, on average - a ruinous rate if you have to walk ten minutes for a toilet, and then queue ten minutes to get in.

On spirits, however, you can keep going, camel-like, for days, without having to urinate once. Others may discover that they have a previously undiscovered anatomical facility, and can simply “seal up” their entire digestive system for the length of a festival; finally releasing the “embargo” at the first service station on the M4, Monday morning. Employees at service stations fight not to have that shift.

Let's keep on talking about the bad things for a while. My favourite “bad festival” anecdote is from a friend, who went to her first Glastonbury with her boyfriend of the time, a practising, albeit “groovy”, Christian. He chose Friday night to take his first acid trip, which very rapidly progressed from “Look! I am touching the colours of my mind!” to “My conciousness is an Escher-like staircase that leads to my red-hot hidden evil!”

Around the time that he started to believe that he was being eaten by a gigantic Satan, she felt the first twinges of a severe urinary tract infection. Declaring their respective parlous states to the medical tent resulted in their being evacuated, in a lights-flashing ambulance, across the area of the Pyramid Stage during REM's headlining set. As you can imagine, the atmosphere in the ambulance was already tense - him repeating the Lord's Prayer over and over, she doing tiny, hot wees into a cardboard potty. Then REM launched into Losing My Religion. Not surprisingly, they split up a week later.

But we should end on a good note, shouldn't we? It's not all Blitz Spirit and cystitis. There is a very simple reason why people go to these things in their hundreds of thousands, every year: you can kind of do anything. Run around screaming, not sleep for three days, come to believe you have learnt to tap-dance while standing on a bin, watch Robert Plant patiently queue for a whole barbecued fish at the Yam The Cassava Caribbean snack-stall. You will find yourself, at 10pm, bouncing up and down to Jay-Z with a couple of friends, screaming along to 99 Problems - even though you don't know a single word of the lyrics. There is as much fun as you can stay awake, or out of an ambulance, for. There are always surprises. That is why you must take your boots.

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