In reply to johncoxmysteriously:
We chose St Johns Head because it was accepted by the RGS as the highest vertical cliff in the UK, and as such it needed to be climbed. I don't know if Kilda is higher, I suspect it is, but maybe not as vertical.
We have since heard similar claims for The Kame of Hoy, but I think thats only 800ft, generally it's a bit arbitrary to what is considered vertical, Certainly the bottom couple of 100ft of St Johns is not vertical but you can make it so by route choice. In THe end what does it matter, they are all bloody steep big cliffs.