Rukun 13 was a secret cell organisation, composed of nationalists, which carried out assassinations of officers of the British colonial government in Sarawak.
This organisation was officially formed at the end of 1947 in opposition to the Cession to the United Kingdom in Sarawak.
After Sir Arden-Clarke was transferred to the Gold Coast colony he was succeeded by Duncan George Stewart.
However, the British decided to keep this information a secret so as not to blame the assassination on Indonesian nationalists and provoke a full-scale war with Indonesia.
[1] After Duncan Stewart was fatally wounded by Rosli Dhobi and later died in Singapore General Hospital, the British arrested all Rukun 13 members by March 1950.