On 1 February 1979 religious leader Ayatollah Khomeini returned to Iran after 14-years in exile.
The most influential leader of the opposition to Mohammad Reza Pahlavi, the Shah, had spent many months while in exile urging Iranians to rise up against the regime.
Just two weeks after the Shah left the country, never to return, Khomeini returned to great fanfare, welcomed by a crowd of over 5 million.
The Shah's government was declared illegal and Iran became an Islamic state under Khomeini's leadership.
Watch the frenzy of his rapturous welcome in this British Pathe newsreel: