BUZZ-RBS: bottom of the FTSE on Goldman downgrade
** Royal Bank of Scotland (LSE: RBS.L - news) falls 2.7 pct after Goldman Sachs (NYSE: GS-PB - news) downgrades to "neutral" from "buy"
** Broker says upside potential increasingly reflected in valuation
** Tangible book value of 0.7x means stock's valuation now in line with sector
** Top faller on FTSE 100