After the assassinations of four of his predecessors, he came to power in September 1843, at the age of five, he was kidnapped by the British Empire, later exiled to Britain at age 15 where he was befriended and much admired by Queen Victoria, who is reported to have written of the Punjabi Maharaja: "Those eyes and those teeth are too beautiful". The Queen was godmother to several of his children.
His mother had effectively ruled when he was very young and he managed to meet her again on 16 January 1861 in Calcutta and return with her to the United Kingdom. During the last two years of her life, his mother told the Maharaja about his Sikh heritage and the Empire which once had been his to rule.
After the death of Maharaja Ranjit Singh in 1839, Duleep Singh lived quietly with his mother, Jind Kaur, at Jammu, under the protection of the Vizier, Raja Dhian Singh. He and his mother were recalled to Lahore in 1843 after the assassinations of Maharaja Sher Singh and Dhian Singh, and on 16 September, at the age of five, Duleep Singh was proclaimed Maharaja of the Sikh Empire, with Maharani Jind Kaur as Regent.
On 13 December 1845 the British declared war on the Sikhs and, after winning the First Anglo-Sikh War, retained the Maharaja as nominal ruler, but replaced the Maharani by a Council of Regency and later imprisoned and exiled her. Over thirteen years passed before Duleep Singh was permitted to see his mother again.
After the close of the Second Anglo-Sikh War and the subsequent annexation of the Punjab on 29 March 1849, he was deposed at the age of ten and was put into the care of Dr John Login and sent from Lahore to Fatehgarh on 21 December 1849, with tight restrictions on who he was allowed to meet. No Indians, except trusted servants, could meet him in private. As a matter of British policy, he was to be anglicised in every possible respect. His health was reportedly poor and he was often sent to the hill station of Landour near Mussoorie in the Lower Himalaya for convalescence, at the time about 4 days' journey. He would remain for weeks at a time in Landour at a grand hilltop building called The Castle, which had been lavishly furnished to accommodate him.
In 1853, under the tutelage of his long-time retainer Bhajan Lal (himself a Christian convert), he converted to Christianity at Fatehgarh with the approval of the Governor-General Lord Dalhousie. His conversion remains controversial, and it occurred before he turned 15. He later had serious doubts and regrets regarding this decision and reconverted to Sikhism in 1886.