In Rolawn Ltd v Turfmech Machinery  Mann J pointed out that:
“It is important to isolate the design in respect of which protection can be properly claimed, and it is vital to ensure that it falls within the definition of design. The Act defines design as ‘any aspect of the shape or configuration – of the whole or any part of an article’, and the right cannot exist until there is an embodiment of the design in an article or in a design document. This combination of features means that design right is confined to what one can actually see in an article – either the physical article or a drawing.”
Ideas are protected by patent law, not copyright or design right. You cannot claim design right for a general concept. It does not give you a monopoly on the idea only a right to prevent copying.
What is an aspect of the shape or configuration of an article?
Section 213 of the Copyright Designs and Patents Act 1988 makes it cleart that design right can be claimed for the design of part of an article. For example a common example is a teapot spout or a teapot handle. An aspect of the design is something that is discernable or recognisable although it does not have to be to to the naked eye and it need not be visually significant. See A Fulton Co Ltd v Totes Isotoner (UK) Ltd  RPC 16.
Does it have to be for the whole of the article or will part do?
This has been termed self selection and presents one of the real difficulties for s213. The courts have recognised this possibility since the early days of design right. Laddie J in Ocular Sciences Ltd v Aspect Vision Care  R.P.C. 289, 422 Laddie J said:
“the proprietor can trim his design right claim to most closely match what he believes the defendant to have taken. The defendant will not know in what the alleged monopoly resides until the letter before action, or, more usually, the service of the statement of claim. This means that a plaintiff’s pleading has particular importance. It not only puts forward the claim but is likely to be the only statement of what is asserted to be the design right.”
But Jacob LJ was clearer in A Fulton Co Ltd v Totes Isotoner (UK) Ltd  RPC 16 where he said “I do not fully go along with Laddie J’s suggestion that what the proprietor can do is to “trim his design right claim”. It is not really a question of “trimming” it is just identifying the part of his overall design which he claims has been taken exactly or substantially. And although Laddie J. was right in saying that the defendant will not know in what the alleged (my emphasis) monopoly resides until the letter before action or the claim form, that does not mean the defendant does not know where he stands before then. The man who copies a part of an article, exactly or substantially, will know what he has taken. It is true that it will be for the designer to formulate his claim properly in any proceedings, but the subsistence of his rights does not depend on how he frames his claim.”