You could go back to 1813 and the Treaty of Gulistan, under which Persia was forced to concede territory to Russia. The treaty was put together by British diplomat Sir Gore Ouseley and is regarded as a humiliation in Iran.

Britain was also instrumental in setting Iran's borders with India in the 1860s.

Then in the 1920s, British forces in Iran under General Edmund Ironside (later British land forces commander in World War II after Dunkirk) helped put Reza Shah on the Peacock throne. His son was Mohammed Reza Pahlavi, the Shah overthrown in the Islamic revolution of 1979, so there is a direct link back to British actions decades ago.

In more modern times, the event that really led to the mistrust of Britain - and the US - was the coup against the elected government of Mohammed Mossadeq in 1953.

During the Iran-Iraq war, which the Iraqi leader Saddam Hussein started, western support for Iraq was deeply resented in Iran.