The correct answer is option 1, Lord Wellesley. The subsidiary alliance was a system introduced by Lord Wellesley during his tenure as Governor-General of India from 1798 to 1805.

Under the subsidiary alliance, the British East India Company entered into alliances with various Indian princely states. These alliances were called subsidiary because the princely states agreed to place their armies under the command of the British and to allow them to station their troops in their territories. In return, the British guaranteed protection to the princely states from external threats.

The subsidiary alliance had several provisions. Firstly, the princely states had to pay for the maintenance of the British troops stationed in their territories. Secondly, the British demanded a share of the revenue from the princely states, often leading to heavy financial burden on them. Thirdly, the British had the right to interfere in the internal affairs of the princely states.

The main purpose of the subsidiary alliance was to establish British political control over the Indian princely states and to expand British influence in India. It was a way for the British to exercise control without directly annexing the princely states.

In conclusion, Lord Wellesley devised the subsidiary alliance system as a means of extending British control and influence in India.