LONDON – Two men appeared in a London court on Tuesday charged under Britain’s National Security Act following last month’s security incident at the Royal Air Force Fairford military base, with prosecutors alleging one tried to assist Iranian intelligence in Britain.

RAF Fairford had been used by U.S. bombers to carry out strikes on Iran, but they were withdrawn on security grounds shortly after five British men were arrested outside the base in southwestern England in the early hours of Sept. 27.

The circumstances of the incident, which remain largely unexplained, attracted huge international attention, coming at a time of heightened concern about the security implications for Western states of the war between the United States and Iran.

U.K.…