Channel 100 on Virgin TV has an advert to promote content on Sky On Demand that's available to Virgin TV customers.
One of the programmes is McMillion$ on Sky Documentaries.
Doing a search on the V6 doesn't bring up anything, and Sky Documentaries isn't one of the Sky channels in the Box Sets menu.
What Package are you on for the TV
As certain channels, programmers are not always available if its not included in your subscription