KPMG warned Guggenheim Partners about weak controls within its business last year, identifying strains in Mark Walter's empire months before a US federal probe into his insurance holdings became public.

The National Basketball Association has banned tech billionaire Steve Ballmer for one year after an investigation found his team secretly funnelled millions of dollars to a star player through sham endorsements that violated league salary limits.

JPMorgan Chase has become more cautious about helping trading firm clients grow as they become formidable competitors to its own trading business. The bank significantly curbed lending to Jane Street last year after the trading firm began making markets in US Treasuries. Jane Street traded over $900bn in bonds last year, generating $40bn in overall trading revenues, just $1bn below JPMorgan's figures. JPMorgan also cut some trading functions for Citadel Securities after the firm announced plans for its own high-touch equity business.

European M&A advisers are dreaming up fantasy mega-mergers to create continental champions capable of competing with American and Chinese companies, though most acknowledge these tie-ups would likely remain dreams.