Hundreds of Iranian radicals stormed the British compound in Tehran last night, replacing the Union flag with a Palestinian one in protest against Israel’s military offensive in the Gaza Strip.

British officials will be assessing whether the security breach, unprecedented in recent years, was an isolated incident or presages further violent demonstrations.

A hardline Iranian news agency said that protests against Britain and Egypt, whose embassy was also targeted, would continue.

Hardline Iranian students have often staged noisy protests outside the British embassy in Tehran, hurling stones and petrol bombs at the building, but Tuesday night’s incident was the first time in decades that they have breached diplomatic territory.

The Foreign Office confirmed Iranian media reports that demonstrators had “trespassed” onto the compound at Gulhak but said the situation had been resolved swiftly and all embassy staff were safe. Iranian police were reported to have intervened quickly to eject the radicals.

British diplomats are maintaining a low-key public stance on the incident - which involved up to 300 people - in order to limit any repeat and robbing the Tehran regime of any satisfaction. But a strong behind-the-scenes protest from London is certain.

The Gulhak compound is a lush and sprawling area several miles north of the historic British embassy in central Tehran. It provides accommodation for diplomats, houses the British Council, a school and a cemetery for the British dead from two world wars.

Iran’s official news agency said: “A large group of people and students entered the Gulhak Gardens, which are occupied by the British embassy to protest at Britain’s policies in supporting the Zionist regime and put up the Palestinian flag there.”

The demonstrators had torched the British, US and Israeli flags, other Iranian media reports said.

There appears to be little doubt that the Iranian regime orchestrated or at least inspired the attack on Gulhak. Just days ago Major General Mohammad Ali Jafari, the commander of Iran’s Revolutionary Guards, suggested his force should facilitate “revolutionary action” similar to the capture of the “Den of Spies” – the US embassy -- on November 4, 1979.

The remarks, made in a speech to hardline university students from a large paramilitary vigilante organisation under his control, were seen as a thinly-veiled threat against the British embassy which has become of the main focus of ire against the West since the American embassy became defunct.

Lambasting “perfidious Albion”, which is often perceived to the “little Satan” pulling America’s strings, is a common pastime in the Iranian media.

Ayatollah Ali Khamenei, Iran’s supreme leader, decreed on Sunday that anyone who died in the defence of Gaza would be deemed a martyr.

Hardline student groups have been urging the Government to authorise volunteer suicide bombers to leave Iran and fight against Israel in response to events in Gaza. There has been no response from the Government. Similar calls have been made in the past but there is no record of any radical ever carrying out such an attack.

There has been a history of political agitation by hardliners against Britain’s ownership of the Gulhak compound, with some calling for the prime chunk of verdant real estate to be reclaimed and turned into a public park and museum for “studying and fighting colonialism”.

One radical insisted two years ago that if the British wanted to keep Gulhak – “a centre of corruption and conspiracy” -- then they “should exchange it for Hyde Park. The Iranian parliament declined his motion to debate the matter.

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