So on my initial modelling point 1 above  lifts the After TAX...

So on my initial modelling point 1 above  lifts the After TAX IRR back to that 25-30% IRR range (centred on 28%).

Fit's with what Bevan said when I asked wouldn't the extra mine life beg the question adjusting the mining rate. 

His answer was they would see it more as lifting the IRR and scenario testing around it. 

(My understanding lifting OZL's decision/resolve to do the project) and strengthening point two above, however that plays out.