In June 2015, how many miles were cycled in one hour by a former Tour de France winner, setting a new world record?

Bradly Wiggins set the record by riding 33.881 miles in one hour breaking the previous record set a few weeks earlier by Dowsett of 32.894.

https://en.wikipedia.org/wiki/Bradley_Wiggins

It is worth pointing out that Victor Campenaerts surpassed Wiggins recorded in an indoor velodrome on April 16, 2019, with a distance of 34.231 miles. I believe he passed a Trabant in the process...

https://www.theguardian.com/sport/2019/apr/16/victor-campenaerts-sets-new-one-hour-record-to-surpass-sir-bradley-wiggins

If anyone wants to watch it during an entire hour:

https://www.youtube.com/watch?v=ICk3aID5xLs&t=4s