By Victoria Gomelsky It is taken as gospel in the jewelry industry that the bold, geometric, diamond-dusted aesthetic of the 1920s and ’30s — a.k.a. Art Deco — is perennially in vogue.

The estimate for this early Art Deco style necklace is £50,000-70,000 but it seems likely that it will sell for more. The emerald necklace has come direct from the family (from Vanessa Nicholson ...