In 1974, MacLehose founded ICAC, the Independent Commission Against Corruption. A mass petition by policemen against prosecutions was an example how bad the situation was. Eventually Hong Kong became one of the least corrupted societies in the world.
In 1979, MacLehose raised the question of Britain's 99-year lease of the New Territories, north of Hong Kong island, with Deng Xiaoping. The talks paved the way for the handover of the entire territory to the People's Republic of China on July 1, 1997. He returned to Hong Kong to attend the handover ceremony.
He was knighted in 1983.
He died in Ayrshire, Scotland.