One rose to the height of British politics, came within a hair’s breadth of becoming Prime Minister and set the nations of Britain’s Empire free.

The other carried out shocking deeds that would rock the establishment, see him branded a traitor and send shockwaves to the very core of his Presbyterian Tiree upbringing.

Politician Iain Macleod and Russian spy Donald Maclean have been described as the “ying and yang” of Cold War politics; both sons of Hebridean stock and with islanders’ gritty determination running through their DNA.

But their seemingly parallel lives, which saw both attend Cambridge University and rise through the ranks of the establishment, would eventually head in opposing directions.

Now a new film is set to explore their backgrounds, their visions about how the world should be, and the intriguing influences that set two islands’ “Macs” on very different paths.

According to presenter Cathy MacDonald, who researched the pair’s lives for the new BBC Alba documentary Macleod MP/Maclean KGB, the two shared a rich Hebridean family history but their political views could not be further apart.

“Donald Maclean, the product of strict Tiree Presbyterianism, ditched Calvinism for Communism. Part of the Philby, Burgess and Maclean spy ring, he became Soviet Russia’s most effective agent and Stalin’s star spy,” she explains.

“Iain Macleod took another path – rising to the heart of the British establishment, becoming an MP, a mould-breaking colonial secretary and chancellor of the exchequer.

“As someone who shares the Hebridean crofting and Presbyterian background in which these men were rooted, I became intrigued by the different paths they took.”

The documentary explores the backgrounds of the men to reveal why they dreamed of changing the world in such very different ways.

Macleod’s parents were born on Lewis and living in Yorkshire when their son was born in 1913.

However, their ties with the island remained strong. The young Macleod attended Fettes College in Edinburgh, then Cambridge.

However, hard work appears not to have appealed to him, and he entered a set of “bright young things”, gaining a reputation as a playboy and professional gambler.

He joined the army at the start of the Second World War, but his risk-taking nature almost ended his career and his life after a boozy session led to a confrontation with a fellow officer that led to Macleod firing his gun at his friend’s door.

Macleod’s experiences during D-Day convinced him to switch focus to help shape the country. Having failed to win the Western Isles seat for the Tories in the 1945 election he won a London seat in 1950 and rose rapidly to become colonial secretary, responsible for granting independence to Britain’s African colonies.

Despite his gambling background, Macleod became chancellor in 1970 but just a month later had a major heart attack and died.

Born in the same year as Macleod, Donald Maclean was the grandson of John Maclean, a cordwainer from Kilmoluaig in Tiree, and his wife Agnes Macmillan.

He embraced communism and while at Cambridge became an agent of the Soviet Union’s People’s Commissariat for Internal Affairs.

“Roland Philipps, Maclean’s biographer, told me that Maclean hated being a spy and compared it to being a lavatory attendant, saying, ‘It’s a terrible job but someone has to do it’,” adds Ms MacDonald.

“That terrible job – betraying his country’s secrets – led Maclean to heavy drinking, a breakdown, flight and exile.”

Macleod MP / Maclean KGB screens on BBC ALBA at 9pm on Monday and repeated on December 29 at 9pm.