If you have bought a tortoise in a foregn country, from a legal and reputable dealer, you may be able to bring it into the UK provided you have all the necessary receipts and proof. You could try contacting the Department for Environment, Food and Rural Affairs (DEFRA) - it's probably best to contact them directly using the link on the right side of the page, as the advice on importing animals has changed a lot in the last few years. You don't have to get a quarantine certificate, but there are restrictions on how many of an animal you can bring (more than 5 requires a special licence) and you will need a special form to show where and when you bought the tortoise(s).

Bringing any tortoise in without the required paperwork is a serious offence. There has been a big problem with tortoise smuggling in the last few years, and DEFRA are very concerned about stamping it out.