Syria will be one of the main topics at next week's G8 meeting, being held in Northern Ireland.
The town of Enniskillen, with a population of 15,000, will also become the temporary home to nearly 9,000 police officers, to protect leaders of the eight big industrial countries.
ITV News Correspondent Martin Geissler reports on the security operation:
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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.