[1] Although MacLehose came from a diplomatic background and lacked colonial administrative experience, he was generally regarded as one of the most successful and popular governors of Hong Kong due to the number of social reforms enacted during his time and for Hong Kong's economic success during his time in office.

Although his tenure as governor finished before formal British-Sino negotiations over Hong Kong commenced, he sought to improve diplomatic relations with China and held talks with Deng Xiaoping.

[2] During World War II, while under the cover of being the British vice-consul, MacLehose[7] trained Chinese guerrillas to operate behind Japanese lines to carry out sabotage.

During one episode, he reportedly walked into a club in Shantou controlled by the Japanese army where he calmly ordered a gin and tonic before leaving without obstruction.

The document contained correspondence between then British Prime Minister Harold Wilson and US President Lyndon Johnson concerning the Vietnam War.

Upon being informed of the potential security breach, Wilson and Brown decided against allowing an investigation into MacLehose's error out of appreciation of his abilities and record.

MacLehose was appointed Governor shortly after the 1967 Hong Kong riots due to his extensive diplomatic background in Asia, perceived skill to analyse political problems and because the British government felt he lacked colonial baggage.

A diplomat with a British Labour Party background,[11][page needed] MacLehose introduced a wide range of reforms during his time in office that laid the foundation of modern Hong Kong as a cohesive, self-aware society.

[12] He oversaw the construction of the Mass Transit Railway, Hong Kong's transportation backbone, and other major infrastructure projects.

[15] Under MacLehose's tenure, Hong Kong faced significant problems with illegal immigration from mainland China due to political turmoil following the Chinese Cultural Revolution.

[5] The talks, although inconclusive at the time, eventually involved top British Government officials and paved the way for the handover of Hong Kong in its entirety, including those parts ceded to the UK in perpetuity, to the People's Republic of China on 1 July 1997.

His various policies were credited with changing the original appearance of Hong Kong, transforming it from a relatively traditional colony into a rapidly developing large region.

In an interview in his later years, MacLehose admitted that during his tenure, he was "committed to rapidly expanding social services and housing supply" in response to the dissatisfaction expressed by citizens during the 1967 leftist riots.

MacLehose was critical of attempted democratic reforms enacted by Chris Patten in 1994 ahead of the Hong Kong's handover.

MacLehose later insisted he did not "give Hong Kong away" to China but admitted out of concern of angering the Chinese government he felt an "obvious sense of powerlessness" in implementing democratic reforms and believed the implementation of universal suffrage for the Hong Kong Legislative Council during his time in office would have intensified conflict between the Chinese Communist Party and the Kuomintang.

MacLehose often emphasized that his mission as the Governor of Hong Kong was to ensure that its citizens led a prosperous and peaceful life.

He was made a life peer as Baron MacLehose of Beoch, of Maybole in the District of Kyle and Carrick and of Victoria in Hong Kong, later that year.

[35] When he was 80 years old, he, alongside former Prime Minister Sir Edward Heath and former Deputy Prime Minister and Foreign Secretary Lord Howe, attended the official swearing-in ceremony of the Hong Kong Special Administrative Region's Chief Executive on 1 July 1997, which was boycotted by the British Government.