He is best known for his close ties with local people, their languages and for surviving the 1763 attack by the order of Nawab Mir Qasim of Bengal, against the British.

[6] He was reported to have made good money whilst in Bengal, including an award of £30,000 as compensation for suffering caused in the siege of Calcutta.

[6][8] Fullerton was a member of a small Company force which was assisting the Nawab of Bengal Mir Qasim in a conflict with Shah Alam.

[7] Following his release he was placed under house arrest in Patna, until under the guise of visiting the Dutch factory, he hired a boat to take him across the Ganges river to Hajipur where some Company troops were present.

He was later accused of misrepresenting a letter written by Nand Kumar to Raja Balwant Singh of Benares suggesting a plot to overthrow Company rule in Bihar and requesting help.