Ann: CGO and Byrnecut optimised mining strategy at Challenger, page-48

Although we can't confirm this completely it would also seem to be supported by the change in focus from the small but "fiddly" remnant mining stopes to the deeper but virgin part of the orebody. Just remember that the change in emphasis on getting to and mining the new lower part of the orebody will require fast development at reasonable costs to bring these new stopes online.

Its not surprising that a mining contractor would have a preference for new development and stopes in preference to working through remnant fiddly stopes adjacent to other old stopes. Whether that's a result of difficulties with these remnant stopes (or problems with dilution and/or grade within them) if we assume that Byrnecut have a fair degree of autonomy/control over what gets mined and when (which we can imply from the actions of Byrnecut and the change in mine plan sequence), then logic would tell us that Byrnecut should be reasonably confident about the tonnes and grade of the stuff that they are targeting in future mining.

The other assumption being no major problems at the mill with gold recoveries, I would imagine that Byrnecut being a underground contract mine operator aren't interested nor would have expertise in running the gold mill.. I don't think the mill has been particularly problematic from memory but someone may be able to correct me on that one.