Trimbuk is located near Nashik and to the north of Pune, and is most famous for being home to the fabulous Trimbakeshwar Shiva temple. The old fortress protecting the town lay atop an exceptionally steep hill.
On April 22, 1818, a British force under Lt. Colonel McDowell invested the fortress and spent three days setting up positions upon the difficult terrain from which they could bombard the fort. They met with heavy resistance, causing much damage to their artillery. However, for reasons that are not entirely clear, on April 25 the fortress surrendered in return for favourable conditions. With this, the vital region north of Pune was securely in British hands.
Interestingly, as an aside, it appears that at some point during the siege, agents of the Peshwa had removed the legendary Neel Mani (‘Blue Diamond’, now named the ‘Nassak Diamond’) from it traditional place adorning the Trimbakeshwar Temple. The Peshwa subsequently handed the diamond over a British officer, Colonel Briggs, who in turn gave it the Earl of Moira, the Governor-General of India, who had it spirited to England, from where it has since been the centre of much controversy and attention.