Don't start too fast but build your speed up over the first couple of miles, settle in to a good rhythm (breathing as well as cycling) and when your legs start to hurt don't back off but hold it and the pain will ease, you can then push it on a bit more until they start to hurt again. Don't worry about sprinting for the finish, you shouldn't have enough left for a sprint if you've paced it well. If you feel okay (relative) then wind it up over the last 4 or 5 miles rather than sprinting for a few hundred yards which will only gain you a few seconds.
Good luck
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