Walker raised the Border Scouts, building on Harrison's force of Kelabits, who had mobilised to help intercept the fleeing TNKU forces from the Brunei Revolt. He also utilised the experience of the Royal Marines as well as knowledge of the skill and usefulness of the Sarawak Rangers in the Malayan Emergency. This was approved by the Sarawak government in May as "auxiliary police". Walker selected Lieutenant Colonel John Cross, a Gurkha officer with immense jungle experience, for the task. A training centre was established in a remote area at Mt. Murat in the 5th Division and staffed mainly by SAS. Border Scouts were attached to infantry battalions and evolved into an intelligence-gathering force by using their local knowledge and extended families. In addition, the Police Special Branch, which had proved so effective during the Malayan Emergency in recruiting sources in the communist organisation, was expanded.