A mirror diamond necklace from Mughal times is expected to attract worldwide interest when it is auctioned next month in London.

Valued at £20 million, the necklace consists of five pendant diamonds that are of table cut or ‘parab’ design with a central stone of 28-carat dimension. Like the famous Kohinoor on the British Queen Mother’s crown, all these five diamonds are from the famous Golconda mines in Andhra Pradesh.

The London auctioneers responsible for selling the necklace are Bonhams, the same company that is also marketing a hunting gun that was made for Maharaja Dalip Singh’s son, Prince Victor Dalip Singh.

Bonhams, which says the stones’ setting is later than their cut, has highlighted the curved sections between the projections as echoing the shallow pointed arches of such iconic Mughal architecture as Humayaun’s Tomb in Delhi and the Taj Mahal in Agra.

Author Katherine Prior, who published “The Maharajahs’ Jewels”, is cited as describing the stones’ setting as “lighter and less intrusive” than India’s traditional “kundan” settings when a stone was embedded in soft malleable gold.

“Kundan” was well suited to stones for which brilliance could be enhanced by foiling”, Prior adds. “But these are diamonds of superb clarity and limpidity. They need no foils and “kundan” might have masked their beauty.”

The precise provenance of this particular necklace is not known, although experts have commented on how some of India’s most beautiful jewels fell victim to colonial plunder.

In 1858 when British troops smashed their way into the Kaiserbagh palace in Lucknow, The Times newspaper’s famous war correspondent from that era, William Howard Russell, reported some of the astonishing scenes. In one case he reported how a solider smashed open a silver box that contained a diamond armlet crammed with emeralds and pearls.

The armlet was offered to The Times journalist for Rs 100, but Russell had no money at the time. Also up for disposal later this summer is a collection of art from the Islamic and Indian worlds that is being sold by Christie’s, another London auction house.

Highlights in the Indian miniature section include an illustration from the ‘Zafarnama’, a history of the post-Mongol conqueror Timor, showing the emperor enthroned (estimated £30,000-50,000) and a victorious allegorical 17th century portrait of the emperor Jehangir (estimated £60,000-80,000).

Christie’s is also responsible for selling Tipu Sultan’s gold ring, captured by the Duke of Wellington after the battle of Seringapatnam in 1799. The ring is cast with the name of Lord Rama and is valued at £15,000.