I have just notice an oil leak from the RS coming from the proximity of the cam oil seal (at the vernier end) - purchased new oil seal thinking that was the problem but when I was undoing the cam bolt that holds the vernier on oil came flowing out of the cam where the bolt locates - i.e. from inside the cam where the thread is ??

Has anyone heard of this before - is it actually possible cause as far as I was aware the cam is made from a solid billet of metal and is not hollow - maybe it is but can anyone help, explain ?? or suggest my next step - I assume remove cam and inspect but I find it hard to understand at the moment