Best bike for a 5 year old?

[RoseberryTopping]

DS is desperate for a red bike, but I'm totally clueless about bikes! What sort of thing should I be looking for? He likes to go fast and won't want something hard to peddle.
I've got a £50 Amazon voucher so would rather get it from there if possible. Any ideas?

How tall is he and what is your budget?

Are those huffy bikes generally quite good then? I'm keen to avoid getting a really heavy one like some of the ones I've seen at the park.

Budget is £100 max, preferably available from Amazon. I need to measure him but he's about average 4 and a half year old size.

The best lightweight bike you can get are Islabikes. But they are expensive!! You might get a second hand one on eBay though. Let me warn you though that even second hand ones are quite expensive. But they are SO worth the price. Absolutely lightweight & beautifully designed - my DD learnt to ride it almost in a day and loves riding coz of it being so smooth & light.

They do have a lovely red!

You can call them for advise - they are very helpful!