From an email conversation with Del Toro's casting director, Jeremy Zimmerman:
'I met today Jeremy Zimmerman, who has done the casting for Guillermo Del Toro’s four films. He’s known Del Toro four six years and says they are 'mates'. I asked him if Del Toro will direct The Hobbit. He was a bit taken back, almost surprised that I would even ask. "Yes, yes, he’s doing it." After a while he said: "He’s got the Ring", and smiled.'
-from an e-mail reporter Jussi Ahlroth from Finland’s Helsingin Sanomat
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