For Sunday's London Winter Run, you are allocated a start time based on the estimated time you gave to complete. I'm not fast, and my 10ks vary from 1hr 12 at my very best to around 1hr 23. Given that there are going to be around 16,000 other people there, I probably said my time would be about 1hr 25 mins. It could well take me even longer as I am recovering from a heavy cold and I hate running in crowds.
My allocated start time is 10:18am.
Imagine my amusement when one of our lovely Beyonders posted elsewhere that his start time is 9:30am and he expects to be finishing by about 10:15am