sentences:  The Sugauli Treaty and Treaty of Titalia returned the annexed territory to Sikkim in 1817.In 1835, Tsugphud Namgyal ceded Darjeeling to the East India Company for an annual fee, but this relationship was broken off after he seized botanist Joseph Hooker and Darjeeling Superintendent Archibald Campbell during their expedition to Sikkim.This led to two British military attacks in 1850 and 1861, resulting in the annexation of Sikkim by 1861.