in the Straits, for example in negotiation for the settlement of Penang Island in 1786 where the Supreme Government remained steadfast in refusing to promise military aid to the Sultan of Kedah. Thus, in a Siamese invasion in 1821, the Penang Government did not offer military aid to the Sultan, but only political asylum and mediation. Indeed the whole history of Anglo-Siamese relations in the Malay Peninsular shows evidence that the non-intervention policy was adhered to as much as possible, (cf. Mills, supra, Chap 8 (Anglo-Siamese relations)) For the obvious political and economic reasons the British did not want to antagonise the Siamese (cf. Tarling, Anglo-Dutch Rivalry in the Malay World, 1760-1824) by interfering in the affairs of the Malay States (such as Kedah, Kelantan and Trengganu) which were within the Siamese sphere of influence.
Severe censures were passed upon Captain Low for his treaty with Perak in 1826; and the treaty between James Low and Perak and Selangor in 1826, received strong criticism from the Supreme Government and resulted in Low's being suspended from his duties. (Tan DE, Supra, p 119) The Indian Government only relented when Governor Fullerton managed to convince it of the necessity of protecting British interests, a clear instance of the Indian Government's unwillingness to intervene in any of the Malay States. This was further proven when appeals of Perak and Trengannu for defensive purposes were likewise rejected. In the Naning War of 1831-2, Governor Ibbetson was told that the extension of territory was not desired. (Ibid. p 119)
An even more striking instance occurred in 1833, when the boundary between the Malacca Territory and the tiny state of Johol was debated over. Between the two lay a debatable piece of land which had formerly been claimed by both states, containing rich mines of tin and gold. Governor Ibbetson regarded the frontier delimitation as an excellent opportunity for showing that accessions of territory and encroachments upon their rights is the furthest from our views and intentions' (Mills, supra, p 177), thus resigning any claims that the British might have to it, and even included it within the area of Johol.
Through the above examples, I would say that the British were pursuing a policy of non-intervention in the Malay States between 1824-73. They upheld this policy whenever possible, though in some cases intervention was unavoidable. And it is significant that sometimes even in instances where British merchants' interests were threatened (for example in Negri Sembilan), the policy of non-intervention was still observed.