William B. Harrison Jr., the architect of what is now the country's biggest bank, on Tuesday offered a resounding defense of megabanks and the good he said they do.

A decade ago, Harrison helped create what is now JPMorgan Chase (JPM) through a series of mergers, including a $59 billion deal with Bank One and its then chief executive, Jamie Dimon. Dimon now runs JPMorgan and has been a vocal industry defender, even as his bank's $6 billion trading loss last year highlighted the risks inherent in large, diversified financial companies.

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