It was supposed to be a Mickey Rourke moment for Lehman Brothers. Like the Hollywood star’s Oscar-nominated comeback performance in “The Wrestler”, survivors of the collapsed US investment bank, in their new roles at Nomura and Blackstone, showed they haven’t lost their touch by advising Chinalco on its complicated $20bn Rio Tinto investment. But a cameo appearance from JPMorgan stole some of the spotlight.

The US giant shocked onlookers by turning up on the deal’s red carpet at the last minute as an adviser to Chinalco, alongside the former Lehman cast and China's CICC. The City’s glitterati were aghast because JPMorgan Cazenove – JPMorgan’s 50-50 joint venture in London – has played Sundance to Rio’s Butch Cassidy for so long. JPMorgan Cazenove is broker to Rio, helped Rio defend against last year’s unwanted takeover attempt by BHP Billiton and has its chairman, David Mayhew, on Rio’s board.

But the conflict catcalls are more “High School Musical” than “High Noon”. Even though Mayhew would have preferred Rio pursue a discounted rights issue instead of the controversial Chinalco deal, he ultimately went along with the rest of the Rio board. The JPMorgan advisory denouement may have stunned wider audiences, but it wasn’t a surprise to Rio. JPMorgan sought and received the blessing of the company’s finance director first.

If anything, questions of conflicts and governance are better directed at Rio and Chinalco than at JPMorgan, which has time and again deftly managed its conflicts.

JPMorgan certainly seems to be ready for its close-up after weathering the credit crunch better than most. Its bit part in the Chinalco deal suggests that last year’s rare league-table trifecta – on the top in advice on equities, debt and mergers – hasn’t left the bank complacent.

But JPMorgan shouldn’t let its success with Chinalco go to its head either. It could have sidestepped all the critics by forgoing advisory credit on this deal - and instead waited for the glory in a blockbuster financing sequel.

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