Those with long memories will recall that Coke's attempt to register the bottle as a UK trade mark under the 1938 Act failed (In Re Coca Cola Co.  1 WLR 693,  RPC 421 (HL) - link to decision here). It had originally been registered as a design, but that expired (in the UK) in 1940, and the House of Lords clearly had public policy concerns about allowing an eternal post-expiry "monopoly" as a trade mark. (The "original" design, according to Wikipedia, was registered as US Design Patent D 48,160).
However, following the demise of the 1938 Act it is now comfortably registered as CTM 2754067. Japan's IP High Court also recently allowed the registration as a 3D mark there.