Collusion in setting gold prices was possible but there is no evidence of this, a senior British markets regulator said on Wednesday. "It is possible but I have no clear evidence that that has actually happened," David Bailey, head of markets infrastructure and policy at the UK's Financial Conduct Authority (FCA), told lawmakers. The FCA is one of several regulators from across the world who have fined 10 banks and brokerages $6 billion for rigging the London Interbank Offered Rate or Libor, a widely used interest rate benchmark.