I like running and cycle to work so I did the London Duathalon about 2 years ago. It was hard but fun - I had proper butterflies before the race! All standard from the elite to the, erm, less so. It's a pricy but well organised race with lots of people, set off at carefully timed intervals.
The toughest bit was balancing the training for me - the course I did was hilly and my route to work and normal runs are flat. I found it particularly hard to do training which was running followed by cycling, though I managed a few the other way round.
Didn't change clothes or even shoes - I don't normally wear cycling shorts and don't have clip on shoes. I used my inexpensive beaten up old commuting bike, and just got some cages put on the pedals as a bit of a token effort. It makes transition more straightforward! As I am in the not-elite category
, I just kept well to the left when riding and let the speed merchants over-take me with room to spare.
Going from the first run to the cycle was nice, actually, to give my muscles a change. The second run after that was murderous, but I'd been warned to expect that, so at least it wasn't a shock.
If I don't get a place in the Royal Parks Half this year, I think I'll do the London Duathalon again.
Let us know how you get on, won't you?