William Low is said to have left behind graphic accounts of how he slew rebels with his sabre and participated in a mass hanging of civilians during the two-year mutiny against British rule more than 150 years ago, the Telegraph reports.
Low also reveals how he came close to losing a hand, cut to the bone and an ear being sliced open in combat during the uprising.
Cameron is on record as saying that his ancestors were involved in "empire building" in India.
Had the full story of his great-great-grandfather's involvement in suppressing the mutiny become public before his recent trip to India, it could have caused diplomatic embarrassment.
Genealogist Nick Barratt, who worked on the BBC programme Who Do You Think You Are, traced the Prime Minister's family tree.
William Low was the grandfather of Sir William Mount, who married Elizabeth Llewellyn in 1929. The couple became Cameron's maternal grandparents.
Low is said to have informed his father, General Sir John Low, that the rebel infantry was thoroughly beaten and dispersed, and added that upwards of 100 dead bodies were left on the field. He said the British casualties were nine killed and wounded, two horses killed and seven wounded.
He said the rebels were left completely dispirited.fficials at 10, Downing Street declined to comment on Cameron's ancestry. (ANI)
Cameron's ancestor slew Indian Mutiny rebels with sabre, participated in mass civilian hangings
