“They took pictures and made notes outside,” Mo Nabbach, who runs the M&M hair Academy in South Ealing, told NBC News' U.K. news partner, ITV News.
The west London salon is just a few miles from the North Korean embassy, which is based in a semi-detached house in a residential street.
Nabbach said the two unidentified men demanded that he take down the poster, which read: "Bad Hair Day? 15% off all gent cuts through the month of April."
"I told them we are in England and not North Korea and told them to get out of my premises," Nabbach added.
London's Metropolitan Police confirmed they had been in touch with both embassy officials and the salon. A spokesman said officers had "spoken to all parties involved" but no action would be taken.
The embassy did not respond to a request for comment from ITV News. However, an embassy spokesman told London's Evening Standard newspaper: "We are not in a position to comment.”
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