Reuters - Britain has summoned the Iranian ambassador to the country to convey its strong objections to the brief arrest of London’s envoy to Tehran on Saturday, a spokesman for Prime Minister Boris Johnson said.

“This was an unacceptable breach of the Vienna Convention and it needs to be investigated,” the spokesman said on Monday. “We are seeking full assurances from the Iranian government that this will never happen again.

“The FCO has summoned the Iranian ambassador today to convey our strong objections.”

Reporting by Elizabeth Piper, writing by Kate Holton; editing by William Schomberg