Here's some colour footage of the cubs to go with the earlier black and white. This is all from between about 6.15 and 6.30 p.m. on May 14th. Looks like the vixen has quite a handful with these four:
I went down again on Tuesday evening, and waited hidden behind some bushes about thirty yards away, downwind from the den, hoping to witness some action. After three hours in the cold and wind, not a glimpse. Must have been my smelly socks that kept them safely underground!