Despite leaving office, he continued to visit Brunei on official business until 1979, meeting with Sultans Ahmad Tajuddin, Omar Ali Saifuddien III, and Hassanal Bolkiah,[3] and developed a deep affection for Malaya and British Borneo.

[a][1] Unlike traditional colonial ambassadors, he approached local authorities with compassion and empathy, often demonstrating more respect than his London superiors preferred.

His amiable relationship with Omar Ali reflected his strategy of "gentle persuasion," which, while not always successful in advancing Brunei toward federation, ensured a lasting connection leveraged by the British government, despite sometimes hindering democratic reforms advocated by his colleagues.

[20][21] Churchill's war cabinet planned to unify Malaya and the British Borneo territories and resign afterward, with the goal of securing victory for the Allies in 1944.

[d] Part of the reason MacDonald was appointed to a position in Southeast Asia just after the Malayan Union proposal failed was because the Malay community there opposed the Sultans' ceding of their authority to the British Crown.

[23] Despite its modest size, Brunei was considered a valuable asset for federation plans due to its sudden wealth from the 1929 oil discovery, which was seen as essential for developing a balanced economy in a bigger state in North Borneo.

He opposed changing the 1905–1906 Supplementary Treaty and recommended the Colonial Office not to associate Brunei with North Borneo or Sarawak as the deadline of 1 July 1946, for the restoration of civilian administration drew near.

[24] Then-Colonial Secretary MacDonald was aware of Brunei's problems in 1940, such as the Sultan Ahmad Tajuddin's postponed official coronation, which he approved despite reports that British Resident John Graham Black was to blame for the delays.

Historian Robert Reece calls MacDonald's writings about the Ahmad Tajuddin, "scurrilous," yet the Sultan was ahead of his time in advocating for more political and financial independence.

In September 1949, after the Sultan's unwillingness to attend the festivities owing to delays in the completion of his new palace, he returned to Brunei in his capacity as the British Commissioner-General for Southeast Asia.

After being eventually convinced by Abang Haji Mustapha, the Malay chief of Sarawak, the Sultan attended, was knighted by King George VI, and conveyed his thanks and concerns in a way that MacDonald described as both diplomatically savvy and comically cunning.

But MacBryan's ambitions to use his relationship with Ahmad Tajuddin to achieve substantial power were dashed, and his attempt to establish himself as Brunei's de facto ruler was quickly abandoned.

He expressed his admiration for Omar Ali Saifuddien III during the new Sultan's coronation, stating that he believed he was the best option for Brunei and for fostering closer connections with Britain.

Historians speculate that Omar Ali eventual resistance to the merger is a reflection of a frequent strategy used by Bruneian Sultans to survive when facing stronger imperial powers.

[29] Records from the British Colonial Office may not always demonstrate MacDonald's sincerity in his devotion to Brunei and Omar Ali, necessitating a closer examination of the parties concerned.

[31] As the initial Commissioner-General, MacDonald vigorously worked toward the establishment of an independent Dominion that included the Federation of Malaya, Singapore, Sarawak, North Borneo, and Brunei.

In order to accomplish his goal of a political federation of Borneo territories ultimately integrating with Malaya, he put cooperative departments, frequent conferences, and officer exchanges into practice.

The notion of federation was abandoned in spite of MacDonald's efforts and diplomatic endeavours due to his lack of governmental authority and the shifting political climate in Britain, which included Malaya's independence movement and changes in British policy.

After receiving a warm reception in Brunei and attending important royal ceremonies, his vision began to wane as new political realities surfaced.

When he visited the Omar Ali Saifuddien Mosque in December 1958, he was allowed into the Sultan's private rooms, where they talked about the possibility of Brunei's royal children receiving an education in England.

[35] Following his retirement from government employment in July 1969, Harold Wilson's administration named MacDonald as a traveling envoy, allowing him to carry on serving Britain's interests by resolving diplomatic disputes between the United Kingdom and Brunei.

[36] Early in 1968, when the new British High Commissioner-designate Arthur Adair was rejected by Omar Ali and the Sultan Hassanal Bolkiah, MacDonald was asked to mediate a diplomatic deadlock between Brunei and Britain.

After visiting the Brunei palace and learning about Omar Ali's complaints, he admitted that the ex-Sultan had not received proper treatment on his last trip to London.

By means of delicate diplomatic manoeuvres, MacDonald managed to win back the trust of the former Sultan and facilitate the restoration of regular ties between the two countries.

[37] MacDonald was instrumental in handling the sensitive issue in reaction to Britain's decision to remove its soldiers from Brunei's protectorate status by December 1970.

He recommended against hastening the notification of troop departure because he was aware of the prospective consequences, which included Brunei's potential economic reprisal and the termination of British diplomatic ties.

In contrast to people like Anthony Abell, who aimed to modernise Brunei's political system, MacDonald concentrated on preserving stability and appeasing the authoritarian inclinations of Omar Ali.

His efforts eventually resulted in a change of leadership in Britain, which paved the way for a revised 1971 deal that gave Brunei complete internal self-government along with continuous British defence backing.

Under the direction of the Research Institute for Products and Islamic Civilisation (INSPIRE), the initiative aims to preserve and study his personal notes, official papers, photos, and letters pertaining to important historical events in Malaya.

[50] He authored the following published works: MacDonald rejected titles and medals despite his lengthy service to Labor and Conservative governments until receiving the Order of Merit in 1969.