 Complete the following phrase:  2015 Six Days of London was a professional track cycling event held at the Lee Valley VeloPark in October 2015. The event was held over six consecutive nights Sunday 18th to Friday 23rd. The event was held in the same Velodrome as used during the 2012 Olympic and Paralympic Games. It followed the typical six-day racing format, involving teams of two male riders competing in a number of races each evening. The primary event in the six day competition is the madison, occurring twice per night, in which teams attempted to lap the field. The overall number of laps determined the winner of the completion, with ties being decided based on points earned in minor races, including the derny, team elimination and time trials. In addition to the main competition, the event featured sprint races, an elite womens omnium held over three nights, as well as junior racing. The first day didnt count towards the main competition, due to a clash with the 