Steephill.tv has a video clip that you can watching via their site. Unfortunately I can’t embed the video directly but that link should take you straight there.
It’s hard to see exactly what happens though you can see the large dog running around the road in the aftermath (when it is immediately put on a lead as an onlooker is thoroughly mortified). You do however see how much chaos is caused by the dog being free to roam onto the road - a fair few riders down and in pain.
After being pulled back from remonstrating with the dog’s owners any further, Phil is then almost hit by a Katusha car to add insult to injury.
It’s one of the joys of the sport that so many can watch it for free but people should always act responsibly. No one wants to see riders or dogs get hurt - even if you have the loveliest dog in the world, keep it on a lead if you bring it along to a bike race!