British officials seized dual-use components destined for Iran's missile industry at the country's biggest airport Heathrow as part of counter-proliferation operations.

Officials said the seizure had now become part of a sanctions enforcement investigation and hope to prosecute individuals or firms involved for suspected violations of the UN sanctions regime.

Iran's long and medium-range missile development programme has undergone rapid expansion, attracting UN sanctions that are designed to thwart the growth of its ballistic missile arsenal. UN reports have verified the use of Iranian-made missiles in the Yemen conflict that have targeted Riyadh airport and other parts of Saudi Arabia.

Iranian proliferation of missiles is not confined to Yemen but also includes other fragile states in the region including Lebanon.

Officials speaking to the London Evening Standard said that the Heathrow Airport bust took place on a shipment of o-rings, the rubber sealant equipment, that were apparently bound for an Iranian oil industry facility.

Monique Wrench, the UK Border Force’s deputy director at Heathrow Airport, said the shipment was stopped when staff became suspicious the rings could be used for making missiles.

“We had a couple of O rings that we identified. O rings are pieces of rubber that go between tubes to stop leakage to seal them. They can be used in oil, but they can also be used for warheads and the like. Our staff stopped them from going to Iran," she said. “It is a component part. It looked like it was going to an oil refinery. But the dots don’t quite join up here.”

A spokesman told the newspaper that British Customs investigators worked “with partner agencies to enforce trade sanctions [on] exports of strategic goods [with] robust enforcement activity against breaches and attempted breaches of trade and export controls”.

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Britain has fought a long-running battle against Iranian-controlled networks set up to procure highly-engineered materials that can be used in the manufacture of weapons.

Andrew Faulkner, a former Royal Marine was jailed in 2010, for the supply of sniper rifles.

A UN panel last week pointed the finger at Iran as the source of missiles fired from Yemen after inspecting debris from 10 missiles. The team found markings that suggested an Iranian origin.

"It seems that despite the targeted arms embargo, the Houthis continue to have access to ballistic missiles and UAVs to continue and possibly intensify their campaign against targets in [Saudi Arabia]," the report said.

The panel said there was a "high probability" that the missiles were manufactured outside of Yemen, shipped in sections and reassembled by the Houthis.