Royal Bank of Scotland (RBS) has culled the number of bidders for more than 315 of its branches down to three rival factions of London investors and private equity groups.The lender is required to sell the branches as a condition of its £45bn taxpayer bailout in 2008.RBS has been courted in recent months by City investors, private equity firms and Spanish bank Santander. Santander had agreed to pay £1.65bn for the branches but the deal fell apart last October largely due to mismatched IT systems. A bid from JC Flowers, the buyout group headed by former Goldman Sachs banker Chris Flowers, and Apollo was also unsuccessful, sources told the Financial Times.The JC Flowers-Apollo bid had proposed making an upfront investment of about £500m in the lender. RBS now has two rival factions of City investors and a private equity group left vying for control of the bank.Among the remaining bidders is a consortium headed by former Tesco Finance Director, Andrew Higginson, which comprises more than 20 asset management companies, including Threadneedle, Invesco Perpetual and Schroders.Another in the running is a grouping of private equity firms Corsair and Centerbridge along with British investors including Standard Life and Lord Rothschild's RIT Capital.AnaCap Financial Partners, a London-based group, has confirmed it is also seeking to buy branches.RD