"British-Iranian relations do tend to go up and down," said Rosemary Hollis, a Middle East expert at the Royal Institute of International Affairs, a major foreign policy think tank in London.

"There are sensitivities that are just part of the landscape," she told AFP.

"The prevalance of the conspiracy theory in Iran that the British are behind everything... You find an astonishing number of Iranians who think that the British even manipulate Washington."

Britain has been at the forefront of calls by the International Atomic Energy Agency (IAEA) for Iran to fully respond to concerns about its nuclear programme by October 31.

Relations have also soured over the arrest in August of a former Iranian ambassador to Buenos Aires, Hade Soleimanpur, who is wanted in Argentina for the July 1984 car bombing of a Jewish community center that killed 85 in the Argentine capital.

Soleimanpur, now studying tourism at an English university, was released on bail last week pending extradition proceedings.

Britain is also pressuring Iran to fulfill its "obligations" to protect its embassy in Tehran, following the third known shooting incident at the mission within a month.

Hollis traced the on-off relationship between London and Tehran to the early days of the 20th century, when the then-mighty British Empire played a major role in developing its oil industry.

Britain occupied part of Iran during World War II, and supplied valuable intelligence to the United States during the 1953 coup against Mohammed Mossadegh, the prime minister who had nationalized Iran's oil industry.

"British-Iranian relations improved in the second half of the 1990s" after they strived to overcome the legacy of Iran's menacing "fatwa" or death order against British author Salman Rushdie, Hollis said.

More recently, Britain was seen as striving to build diplomatic bridges with Iran -- branded by US President George W. Bush as part of an "axis of evil" -- in a clear bid to lend support to reformists in the Islamic republic.

Gary Saymore, director of studies at the International Institute for Strategic Studies in London, said he believed Iranians were looking at Soleimanpur's arrest "as part of a bigger conspiracy" by the United States and Britain to put pressure to bear on Tehran.

"Tehran has a very ambivalent relation with the United Kingdom," he told AFP on Tuesday.

"On the one hand, they hope that their relationship with the UK will help reduce American hostility," he said. "On the other hand, the UK is a 'little Satan,' seen as a potentially hostile ally of the United States."

Saymore, an expert on non-proliferation, believed Iran is "still a few years away" from being able to develop nuclear weapons.

"From their standpoint, it makes more sense to cooperate now to buy time, so that they can complete their (nuclear) facility under IAEA safeguards and under the Non-Proliferation Treaty," he said.

"Once they leave the treaty, that obviously exposes them to political pressure and even military attack coming from the United States and Israel," he added

In any event, Iran's attention now is primarily on domestic politics, Saymore said.

"There are going through a period of adjustment... They are obviously some very serious internal strains (and) they would like to have peace and quiet so they can focus on domestic issues."

WAR.WIRE