No, prototypes or drawings are not requiered at this stage to register your idea. They may be needed at a later stage for explenation purposses (if applicable).

For your own benefit we recommend that you document and copyright whatever you have in your mind so that it stays fresh and new as well as secure. 

Keeping copies of all your drafts and any other material as you develop it could be useful evidence if you have to prove you are the origional author. Sending a copy of your work to yourself by Special Delivery Post and not opening the the envelope on its return will also help.