New Delhi, July 14 -- LONDON - The festival had drawn fifteen thousand Ahmadiyya Muslims to a farm in rural Suffolk when police moved. On Sunday, counter-terrorism officers executed coordinated arrests across England and Wales, detaining twelve people linked to an alleged far-right plot to attack one of Britain's largest Islamic gatherings. Officers said they had undoubtedly saved lives.

The Ijtima, an annual congregation held by the Ahmadiyya Muslim Community, had been drawing worshippers from across the United Kingdom when authorities became aware of a credible threat to the event. Police contacted organisers and the gathering was brought to a close early, its spiritual programme cut short by a terror investigation that spanned multipl...