As Don Argus ponders whether to step down as BHP Billiton chairman at the miner’s annual meeting in two months he can do so knowing the long-term goal of combining its Western Australia iron ore assets with those of Rio Tinto is closer to reality.

News of the iron ore joint venture, valued by UBS at $116bn-$126bn, was overshadowed last Friday by Rio’s decision to ditch its proposed $19.5bn tie-up with Chinalco and launch a $15.2bn rights issue.