Fastest sprinter and their top speed? What is the top speed hit during a sprint on flat ground in a road race by a professional sprinter, say, someone like Cavendish?

Is there an official record for this and if so who holds it currently?
Not a complete answer really, but I've had a scan through this TdF data Twitter account and Greipel's winning speeds from his two wins this year are an average of 59.58 km/h over the last km and a peak speed of 67.03 km/h.

Pretty quick.

Edit: more stats for nerds here.