Speaking to reporters outside his home in Surrey, Zaid al-Hilli said it was "good news" that he would not be charged in connection with the murder of his brother and that he was "relieved".
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The Labour leader did not say whether he would maintain Britain's nuclear deterrent programme.
Ukip leader Paul Nuttall also said he would want to get rid of Sharia courts.
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.