The 1,250 fundraisers set to take on tomorrow's OX5 Run have been reminded that the clocks go forward tonight.
Thousands of runners, spectators, family and hospital staff will gather at Blenheim Palace from 9am in aid of Oxford Children's Hospital.
But, as is the case every year, the clocks go forward on the eve of the run.
British Summer Time officially starts at 1am - that means as soon as clocks hit 1am it will be 2am.
Runners and spectators should set their alarms an hour earlier.
The run will start at 10.30am and the starting klaxon will be sounded by six-year-old Anna Drysdale and eight-year-old Noah Castro, who have both been regulars at the hospital battling cancer.
The annual event began in 2003 and this year could break the £1m barrier for funds raised in its history.
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