Reply to comment:

I blogged about this effect two years ago: On the Vienna exchange point, the live TV streams can make a significant change to the average traffic flow. There is a lot less baseline traffic compared to LINX and I also assume that the BBC is doing either private peerings with the big ISPs or has deployed a CDN into their network to reduce the network load. In Austria -- AFAIK -- our public broadcasting organization pushes all their data via the VIX. Combined with the lower baseline, this created nicely visible peaks. We'll see the same effect in the winter again: all the live-streams of alpine skiing events: They are popular in Austria and a good number of them are during business hours.