Letter to Shabana Mahmood describes controls that could block British dual citizens’ entry to UK as ‘unacceptable’ Letter to Shabana Mahmood describes controls that could block British dual citizens’ entry to UK as ‘unacceptable’ The Liberal Democrats have called on the home secretary to “move at speed” to delay the rollout of new border controls that could result in British dual nationals being blocked from entering the country. A letter sent by the party to Shabana Mahmood echoes one sent by