The British appointed Raja Bilah penghulu of Blanja while his son Raja Yacob became penghulu of Tronoh, which generated large revenues after the opening of the Tronoh Mines, the largest tin producer in the world in the 1920s.
The appointment of Raja Bilah as penghulu of Blanja and his son Raja Yacob to the position of penghulu of Tronoh by the British led to significant revenue generation from the opening of the Tronoh Mines in the 1920s, which was the world's largest tin producer.