It's slippery outside people!

Single speed with rear brake. They were thinking of the children, less chance of them going over the bars. There is also something in the headset to stop barspins.
Check out the website.http://www.islabikes.co.uk/

They have changed the set up on this. Previously it had a front brake and rear hub break operated through the pedals. The rear hub brake is great for small kids. The front brake was a bit of an issue as it didnt have the headset bit and as a result the cable has frequently been ripped out of the caliper when she bar spins (generally a result of chucking the bike down and picking it up again without looking...). This keeps dad's diy skills busy!

I am surprised that they have changed this set up as I am not sure 3/4 years old have the hand strength to stop themselves on anything resembling a gradient, particulalry if they only have a rear brake.