Also it'll be unbelievably cold in there and the thing I'm probably most worried about is my face. That sounds silly but it's very difficult, if you're in cold temperature water, to get your head under because it takes your breath away. And then your hands go numb so you try and wriggle your fingers while swimming to warm up. It's very tough.

The transitions will be tough because of the nature of a triathlon, you have to get changed and dry off or whatever. But this is going to be even harder because I have to do all that, then speak on the radio, do an interview with local telly, do some press and some interviews.

At the end of October I started doing a bit more swimming and learning how to swim properly, because I hadn't really done it since I was at school. Then I really accelerated in December and for the whole of January's I've been doing at least one thing a day - normally a swim and a cycle, or a swim and a run, every single day.

There's a balance and I feel very, very strong and very, very fit at the moment. There's no - touch wood - niggles at the moment, there's nothing that's twinging or nothing that's too painful. Apart from a bit of chafing from the wetsuit!

There's going to be a lot of eating. My listeners have tweeted me and said "You've just got to keep eating, keep your energy up and have someone on duty to give you a massage if you need it." It will be a case of getting it done and making sure I don't get too cold, because that's crucial for the muscles. So that's all going to be taken care of. But really there's not much you can do - if you start cramping up you've just got to get on with it.

'm starting to get a swimming physique, which I'm very pleased about, because for me that's the most appealing male physique. It's not show-y off-y Mr Muscle, "Look how much I can bench." It's just a real lean, athletic figure and it doesn't look like you try too hard. When you see people who have huge biceps, it looks like they're in the gym all day. But I think there's a difference between looking muscly and being fit.

What's most troubling is the open water swim. It's windy, the waves are getting in your face and the water is a bit dirty. And there's silly things like you can't touch the bottom if you swallow a mouthful of water.