Egypt's Interior Minister, Mohammed Youssef, told BBC Arabic that vote-rigging in the election would be impossible. He said that judges overseeing the polling stations would start counting the ballots on Thursday, watched by representatives of the candidates.
The ballot boxes will then be sealed before being taken to the Higher Presidential Election Commission (HPEC). He also said that "no crime" has been reported on polling day.
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Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.
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