The jeweller also made Kate Middleton’s sapphire engagement ring, which previously belonged to Princess Diana.
Charlotte added: “It appears to feature a large two carat oval diamond, complimented by two 0.4 carat trillion shaped diamonds on either set, set on a white gold band.
“At 77 Diamonds, an engagement ring of this style and quality – a D or E colour grade, and VVS clarity – would typically cost approximately £20,000.
“If purchasing this specification of ring at many other Mayfair jewellers, it would be priced in the region of £35,000.
“The style of engagement ring is known as a Trilogy ring.”
According to the expert, it has a very special meaning.
Charlotte said: “Traditionally, three central diamonds are said to represent the couple’s past, present and future, making it a very romantic and meaningful choice of design.”
Sophie also has a number of other rings in her collection although will always wear her engagement ring paired with her wedding band.
Kate Middleton’s sapphire engagement ring, which is one of the most recognised rings around the world, is said to be worth a fortune.
Kate Earlam-Charnley, Design Director at Taylor&Heart said: “The royals have always led the way in terms of jewellery, especially engagement ring design.
“Kate Middleton – if she’s wearing it, everyone wants it! The Duchess of Cambridge wears Diana’s engagement ring as a sweet way to ensure Diana is with them at all times.”
Experts have valued the Duchess’ ring at around £400,000, though others say that given its history, could be worth a lot more.