"Coles is never going to cut it on a ROC basis, because WES have...

"Coles is never going to cut it on a ROC basis, because WES have their stocking stuffed full of goodwill from the original purchase."

Sure, but as you rightly imply, the ROC that WES generates out of Coles is largely an accounting oddity which is mainly reflective of a certain capital investment decision made a decade ago. So, that legacy decision is represented by today's sunk capital.

But for an ongoing shareholder value creation standpoint, the real question is what kind of ROC does Coles generate on the incremental capital that is invested in that business. IT is clearly higher than FY2017's 9% (FY2016 = 11%) figure that WES quoted (because that figure includes the acquisition goodwill).