“I think it just reflects the really quite bizarre view that Ahmadinejad and his supporters have,” said Professor Ansari, whose father was an Iranian diplomat under the monarch ousted in 1979, Shah Mohammed Reza Pahlavi. He added, “Britain has always been a bogeyman, but going back to that now, resorting to the villain of choice, if they really believe it, just shows how out of touch they really are.”

Iranian popular culture has kept alive suspicions dating to the 18th century, when Britain, protecting its empire in India, began competing with Russia for influence in Iran. Britain’s strategic interest deepened with the development of Iran’s oil fields.

Antipathies sharpened when Britain invaded Iran in 1941 and exiled the Iranian ruler, Reza Shah Pahlavi, suspected of pro-German sympathies. In 1953, British secret services worked with the Central Intelligence Agency to overthrow Mohammed Mossadegh, the nationalist prime minister. The issue then was the Mossadegh government’s nationalization of Iran’s oil fields, ending the monopoly of the British-owned Anglo-Iranian Oil Company.

More recently, Britain’s relations with Tehran were strained by the confrontation over the author Salman Rushdie. His novel “The Satanic Verses” prompted Ayatollah Ruhollah Khomeini, leader of the Islamic Revolution, to issue a call in 1989 for Muslims to kill Mr. Rushdie for what the ayatollah deemed to be the book’s blasphemy. That led to a lengthy freeze in diplomatic relations, and to years in which Mr. Rushdie, a British citizen, lived in hiding under police protection.

But perhaps the sharpest thorn in Tehran’s side has been the BBC’s Persian-language services, by radio since the early 1940s, and by a recently established television channel. Millions of Iranians have come to rely on the BBC’s reporting on Iran, regarding it, Professor Ansari said, as the “most trustworthy” account of what is happening in their country.

On Friday, the BBC said it had decided to use two extra satellites to combat intensive jamming efforts by Iran, a step likely to be seen by Tehran as a direct challenge, given its assertions in recent days that foreign broadcasters  and Web services like Facebook and Twitter  are being used to foment unrest over the disputed election.

But Rosemary Hollis, a professor of Middle East studies at City University London, said Mr. Khamenei’s attack on Britain may have been prompted by something more basic to the Iranian psyche, an old shibboleth in which Britain remains the dark force behind American power. “Strange as it seems, they’re convinced that the British are the clever ones, manipulating things behind the scenes,” she said.