The son of one of the GAA's founders has been uncovered as the inspiration behind the original Big Brother after hiding his Irish identity to become Winston Churchill's closest aide.

A new RTÉ documentary will attempt to unravel the extraordinary life of Tipperary publisher Brendan Bracken, who became Churchill's right-hand man by duping his way to the top of British society in the 1920s.

In the documentary, the Walter Mitty-style fantasist, who became one of the most influential Irish people of the 20th century, is credited with securing Churchill the job of prime minister.

It reveals that one of the most famous monikers of the 20th century – Big Brother – was based on his real-life persona as minister for information in Britain during World War II.

The son of an Irish republican – largely unknown in his native country – rose to these extraordinary heights during the war after claiming to be an Australian orphan when he talked his way into an English public school in 1920.

In the documentary, Churchill's Irishman, distant relative Adrian Bracken traces the web of lies which started when Brendan Bracken was exiled to relatives in Australia by his widowed mother at the age of 15 because of his unruly behaviour.

He said: "Brendan Bracken was Winston Churchill's closest friend and adviser for over 30 years but Brendan Bracken was also a compulsive liar and a complete fantasist.

"He tried to hide himself from the pages of history by ordering all his papers burned after his death."

The documentary reveals that Bracken was appointed first lord of the admiralty after World War II, a post held by Churchill in World War I.

The charismatic, flame-haired Irishman is credited with being the ultimate political fixer who vaulted Churchill into the prime minister's role.

In 1940, Bracken warned the very vocal Churchill not to speak during a crunch secret Conservative meeting to elect a new leader when Chamberlain was on the way out.

Lord Halifax, the foreign secretary, was the obvious choice as the next prime minister and Churchill was likely to support him but Bracken warned his friend not to speak if he was asked to back Halifax.

After a two-minute silence by Churchill in answer to Halifax's nomination, Churchill was asked to step into the role and he accepted.

"It was very unlike Churchill to say virtually nothing. Whoever told Churchill not to say anything deserves the credit of history and we believe that man was Bracken," said Eunan O'Halpin, professor of contemporary history at Trinity College Dublin.

Former publisher Bracken had always turned down government positions but in 1941 he became the reluctant minister for information to counter the Nazi propaganda machine.

"As minister for information he was in charge of giving his fellow newsmen the stories they wanted," said Adrian Bracken.

"He employed several leading writers including Eric Blair who, as George Orwell, later satirised his time there in the novel, 1984.

"Brendan Bracken, or BB as he was known around the ministry, believed the truth was so important that it must be protected by a bodyguard of lies, and that became Big Brother.

"Room 101 and the Ministry of Truth have all passed into the modern English language."

The documentary reveals that, before he became prime minister in 1940, Churchill had financial problems and was almost forced to sell his beloved Chartwell country estate.

The Irish publisher solved his money worries by selling Churchill's writings and articles and setting up a Churchill fund in 1938 which helped to pay off his debts.

Bracken, who was born in Templemore, Co Tipperary, in 1901, was the son of staunch IRB member and one of the GAA's founding fathers, Joseph Bracken, who died when Brendan was just three years old.

"JK Bracken was one of the founders of the GAA and a major nationalist figure towards the latter end of the 19th century – again a man of huge drive and ambition and power," said Brendan Bracken, the nephew of Brendan Bracken senior.

"I often wonder if JK had lived would Brendan have been out in 1916," he said.

Brendan Bracken – Churchill's Irishman will be shown on RTÉ One on Tuesday, 21 December at 10.15pm