When Clive left Bengal for the last time, on 26 January 1767, Reza Khan was at the height of his power, the essential key to the system Clive had created. The basis of Clive's system, as he explained in the minute of instructions written for his successor, was that the Company's servants should always remember ‘that there is a Subah [Subahdar] … and that the revenues belong to the Company, the territorial jurisdiction must still vest in the Chief of the Country acting under him and this Presidency in conjunction’.

By the phrase, ‘the Chief of the Country’, Clive meant Reza Khan, whom he saw as the indispensable link between the Nawab and the Company. Sykes, the co-author of the scheme and a principal executant of it, equally held Reza Khan's to be the vital role, saying two years later, ‘I should be really at a loss to point out where we could find a man who would fill his station with equal dignity and propriety’. The Khan and the political system were therefore inseparable. If the system failed and the Calcutta government ceased to be united behind it, Clive's towering personality being withdrawn, Reza Khan had to fall too.

Initially the system worked well; under Verelst and Cartier the Company's foreign relations, both with the Indian rulers and with the other European nations trading in Bengal, were conducted through the Khan and in the name of the Nawab.