Thousands of people are expected to run or walk around the grounds of Harefield Hospital in the annual fun run this weekend.
Former light heavyweight boxer, John Conteh, will be launching the runs, of which there are three distances.
The Harefield Hospital Fun Run and Family Day will take place on Sunday.
The 10km run will begin at 10.30am and the 5km run and short jog will both start at 11.30am.
The event is in aid of Harefield Hospital to help raise money for the specialist heart and lung unit, based in Hill End Road.
Organisers expect this year’s event to be one of the biggest, with a dog show, fancy dress competition, arts and crafts stalls, children’s race and a medieval re-enactment.
Entry on the day costs £20 for adults and £10 for children, which includes a race T-shirt, medal and drink.
All money raised from the event will go towards the Harefield Heart and Lung Appeal.