LONDON (Reuters) - Britain is working “virtually around the clock” to secure the release of British-Iranian aid worker Nazanin Zaghari-Ratcliffe and other dual nationals held in Tehran, Prime Minister Boris Johnson said on Wednesday. “We’re working virtually around the clock to secure the release of all the dual nationals that concern us in Tehran ... We’re doing everything we can to secure the (end to) what we regard as the completely unjustified detention in Tehran of Nazanin Zaghari-Ratcliffe,” he told parliament.