“The result of this special tender affirms the very high value placed on blue diamonds, which are undoubtedly one of nature’s rarest treasures.

"We believe this to be the first time that five rough blue diamonds of significant size, colour and clarity have been offered for sale at one time and we are delighted that the collection has been bought in its entirety,” says Petra CE Richard Duffy.

The five Type IIb diamonds, weighing 25.75 ct, 21.25 ct, 17.57 ct, 11.42 ct and 9.61 ct, were recovered at Petra`s Cullinan mine, in South Africa, in September.