What is the smallest tortoise?

[N4S]

and how big does it get?

[MPenn]

If I remember correctly, it is the Egyptian tortoise, Testudo kleinmanni.

If you can find any captive bred, they are fairly expensive.
Males have a Straight Carapace Length of 95 mm or ~ 3.74 in. and the largest female had a SCL of 127 mm or ~ 5.0 in.

[kurgan]

They are nearly extinct in the wild and not very numerous in captivity. Please don't support this by buying them - it is probably illegal in most locations anyway.

Here's a pic of a hatchling from the BBC - HOTM I'd say if it wasn't a professional job!
http://news.bbc.co.uk/nol/shared/spl...0288/img/1.jpg

[MPenn]

They are nearly extinct in the wild and not very numerous in captivity. Please don't support this by buying them - it is probably illegal in most locations anyway.

I don't know about the UK, but here in the States, they are not illegal. You can find legally CB babies for sale when they are available.