John Mack, the former CEO of Credit Suisse Group AG (NYSE:CS), reportedly heaped praises on UBS Group AG (NYSE:UBS) Chairman Colm Kelleher, saying the banker is smart and is a natural leader.

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Relationship: Mack also reflected on the time he spent at the Swiss lender and talked about his relationship with the bank.

"They said I am the most arrogant person they ever met and I said they are the stupidest people I have ever dealt with. So we had a great relationship. As soon as my contract was up they shot me. So it was fine," he said in the interview.

The former Credit Suisse CEO also voiced his opinion on what Swiss banks should be focussing on going forward. "They’re great banks, they just needed to open up the vault a little more and not be so secretive," he said.

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