In this role he was responsible to the governor-general, the Marquess of Dalhousie followed by Lord Canning, for the safety of Fort William during the Indian Rebellion.

[5] Lord Canning offered him the post of Governor of the Straits Settlements on 1 July 1859, In recognition of his services during the rebellion.

[6][7] Under a royal charter of 1826, Singapore, Malacca, Penang and Dindings had been combined to form the Straits Settlements.

The Governor had little formal power, but was able to influence the Calcutta authorities who relied largely on the recommendations of these representatives on legislation and policy in each settlement.

On 5 December 1866, he received unofficial word that he was to be removed from office on 1 April 1867 and resigned the commission himself on 15 March 1867.

Cavenagh was appointed Knight Commander of the Most Exalted Order of the Star of India (KCSI) in the 1881 Birthday Honours on 24 May 1881.