To bring it back to the subject of refereeing, Chris Joynt's voluntary tackle. What should have happened?

But if the ball is clearly on the ground, which it was, then surely a try has to be awarded. You can't say "Well the ball was on the ground, but it was a pretty good defensive effort to try and stop it so we won't give the try."

We had a few last season.

There's a difference between the ball, clearly being on the ground and how it got there.
you can't just award a try because the ball is on the ground, or at least in my opinion you can't, but it seems anything goes these days.

King went into the challenge and for the line with full possession of the ball and shortly after the ball could clearly be seen on the ground. There was absolutely no evidence whatsoever that King had at any time lost control of the ball and I'm assuming, because he awarded the try, that the referee at no point called held. Maybe it was a great effort by the Catalan players to prevent the try, but it wasn't enough. Having the try awarded by Child before being passed up there was absolutely nothing the VR could have seen to disallow it.

You suggest that good defence should be rewarded, but shouldn't a good, strong, determined and ultimately successful attempt to ground the ball be rewarded too?

both defence and attack should be rewarded, but when there is no evidence that he actually grounded the ball then, the defending side should get the B.O.D, for me, anyway.