Dozens of competitors are also thought to be planning an attempt at a Guinness World Record while dressed in fancy outfits like a suit of armour or a Paddington Bear costume for the marathon, reports the Independent.
Organisers have warned participants to consider dropping their target time and rethink costumes in view of the Met Office's prediction of "strong sunshine" and "very warm" weather, reports I News.
"We want to stress that there will be plenty of water available and runners should drink according to their thirst and use spare water to douse their head and neck," said marathon event director Hugh Brasher
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