'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.

You wouldn't run a marathon the day before you run a marathon, you need to leave some sort of surprise for your body.

I just have to deal with it [injuries] if and when problems happen. It's obviously a concern and I've been very careful with my training, making sure I warm up and warm down before everything and not pushing myself too stupidly.

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.

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.

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.