TV delay pictures between Sky and Virgin media.

I got a whisper of a gamble going down today which was Doncaster 3:30 Sicur. I told my brother to get on it and while the race was running we were on the phone to each other. Me watching on Sky, my brother watching on Virgin media and his pictures were a good 4 or 5 seconds behind mine.

So my question is how many seconds are mine behind? And who has the fastest pictures out of interest?