"At the start of the brevet, the group will promenade out of town together for the first 2 to 4 miles, whereupon you may ride at your desired pace" [1]
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"Before I finish uttering 'off you go' there will be a scramble and half the pack will head off hell for leather, while the other half are still powering on GPS's and working out which way to turn out of the car park"
[1] - never seen it in a UK info sheet, but seems very popular over here in USA