Watts was chief of the
Cossimbazar factory (trading post) of the East India Company.
Robert Clive made Watts the company's representative to the
Nawab's court at
Murshidabad. Clive engaged Watts to work out a secret plan for the final overthrow of
Siraj ud-Daulah and to install a favourable ruler instead. Watts thus set up contact with the dissident
emirs (nobles, commanders) of the Murshidabad
durbar (court), including
Mir Jafar, Rai Durlabh and Yar Lutuf Khan. Watts played a role in forging the grand conspiracy against Siraj Ud Daulah which led to the
Battle of Plassey. On 5 June 1757, he visited Mir Jafar and obtained his oath of allegiance. In recognition of his services, Watts was given £114,000 from the Nawab's treasury and made the governor of
Fort William on 22 June 1758, in place of
Roger Drake, who had deserted the fort when it was attacked and captured earlier that month. This had been the location of the
Black Hole of Calcutta on 20 June 1756. Four days later Watts resigned in favour of Robert Clive to return to England. ==Later life and death==