In 1866, Raja Abdullah leased Klang to two traders from the Straits Settlements: William Henry Macleod Read and Tan Kim Ching. Among the benefits of the lease was tax collection from the opium trade, in which Raja Mahdi was involved. When the two traders went out to collect tax, including from Raja Mahdi himself, he was offended as he felt he should be exempted from the tax since he was of Selangor royalty, and refused to pay. Raja Abdullah saw this as an act of defiance by Raja Mahadi towards him. This incident, exacerbated by Raja Mahadi's continued dissatisfaction with being ignored as the successor to Sultan Muhammad for the Selangor throne following his death in 1857 in favour of the then Raja Abdul Samad (later became Sultan Abdul Samad), and further conflicts between their followers worsened the already tense relationship between the two antagonists, which many believe were the initial causes for the outbreak of the Klang War.