He also faced an illegal attempt by an immigration officer at the airport in Nairobi last week to block him from flying to neighbouring Tanzania, he said.

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Sheardown was an immigration officer at the Canadian Embassy in Tehran when students and militants stormed the U.S. Embassy there on November 4, 1979, taking more than 50 Americans hostage.

CNN: STORY HIGHLIGHTS

Embarkation controls - which meant people leaving the UK were seen by an immigration officer - were ended in 1994 for those travelling from ferry ports and small ports to a European Union destination.

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Now, the requirement that a police officer must determine the immigration status of an individual who they have a "reasonable suspicion" is in the country illegally extends to those instances where police respond to something as minor as city ordinance violations.

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