Originally posted by peekay4
I believe they restored (partial) attitude & heading information only after the decision to divert to Melbourne was already made.
Possibly so, but the report says "The flight crew continued their attempts to restore the flight guidance and navigation systems while in the Sydney area. The FO then carried out the IRS ALIGNMENT IN ATT MODE checklist from the QRH, restoring some ND and PFD functions..." So it seems they were still in, or very close to the Sydney area when those functions were restored. They were certainly much closer to Sydney than Melbourne! The weather in Sydney at the time was 10k vis, light rain showers and a cloud base of 1,700ft, so they would have been visual well above the minima.