Woman in a blue jacket setting an absolutely cracking* pace along the towpath from Hermiston to Slateford (well, I thought so and I reckon I set a fair pace myself) on an interesting looking drop-handle black singlespeed at around 5pm.
Probably someone on here, judging by the rather specialised nature of the bike.
*For the record, she (and I) took all the dangerous bits carefully and at reasonable pace, but opened up the throttle on bits with clear sightlines and no other traffic.