Attempt number two, and this time we were serious! We had Simon's mum in tow, which meant that we could "leave a car at each end", as was suggested, and do CC4, CC5, and CC6 in one go.
We parked on the Risca side of the hill and walked up the track to the top. It was a marvellous, sunny day with good, if hazy, views; and, this time, success: Simon found the cache straight away. From here, we headed back down the track and onwards west along the ridge towards CC5.
Thanks for this lovely location!