By repute purchased in Hong Kong in the 1950s or '60s, it has a gently flaring body delicately decorated with four pairs of ruyi-heads separated by florets extending to leafy tendrils.
Other wine cups of this delicate design are in the Percival David collection, while Sotheby's and Christie's have also both sold pairs in Hong Kong in recent years.
At the auction on May 20-21, it was hammered down at £340,000 against a £100,000-150,000 estimate.
The buyer was a Chinese private collector - and "a sea of phones" were taking pictures of the bidding, say W&W.
The buyer's premium was 20%.