Thanks Trevor.
I don't want to detract from the debate on the other thread (and I do agree with Mark on this), but when barbel fishing I rarly use an unhooking mat. My opinion is that wet grass is just as good and probably removes less slime. Its also cooler and fish tend to slide less (just try using a mat on a sloping flood bank).
Most fish that I catch under about 8lb are unhooked in the net or lifted just long enough to unhook them then placed back into the water. Bigger fish are laid in the net on soft grass or if the bank is at all muddy in my net on a carp sack. Barbel aren't as prone to internal damage as carp as they are a lot more muscular so I don't see the need to use a padded mat. The photo that I assume your comment is about was taken in that position because I noticed how the colours complemente the fish. The fish was kept in the net until I was ready and then laid on the soft grass for the picture.
The exception to this is if I'm fishing the Trent, when I always bring a mat as I may be fishing on a rocky bank or a rough gravelly beach.
Tools like unhooking mats are there to help, not to be used slavishly without thought. In some instances you're better off not using them.