Anchor Road, Canons Road, Canons Way, Lower College Street, Bridge Valley Road, the Portway, some roads around the Cumberland Basin System and others will be closed early morning until mid-afternoon.
The race starts at 09:30 from Anchor Road, Harbourside.
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Jeremy Corbyn's visit has been one of the big talking points of another busy day at Glastonbury.
The Labour leader said socialist politics would not be put "back in a box" as he appeared on stage at the festival.
Turning windier with a few showers