Road closures for the events are in place in Southgate Avenue (A2004) both ways between the A2220 and Hawth Avenue.
The International Half Marathon and Corporate 5k events are being followed by a Family Run this afternoon.
Neil Boniface was first to finish the half marathon with others celebrating their times on the 5k challenge.
Among those who took part in the half marathon are St Catherine’s Hospice, St John’s Church Crawley and Sussex Newspapers own sports editor Mark Dunford.
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