While Pippa's engagement ring is slightly smaller than her sister Kate's - and carries a lot less history - it cost much more.
Believed to be made to order, it is very much in the Art Deco style of the 1920s and 1930s.
Experts say it is almost certainly made in platinum and has a three-carat Asscher-cut - or square-cut - diamond.
This is surrounded by smaller round brilliant diamonds in a rub-over or bezel setting, in which the stones are held in place with a rim of metal, a more secure arrangement than the traditional setting and ideal for a sporty young woman like Pippa.