British FTSE 100 index retreated from gains on Tuesday as investor optimism over ultimate Greek debt crisis solution was offset by fears Greece would be forced to ask for more funding or default. British index slipped 0.3% during session weighted down by oil and financial shares. Tullow Oil Plc posted the biggest loss for the index, tumbling 4% after the company reported results of the Sierra Leone exploration well. BP PLC dropped 0.4% ahead of oil-spill trial due next week. Lloyds Banking Group PLC edged down 1.8% and Royal Bank of Scotland Group PLC fell 1.5%. At the moment of writing FTSE 100 is 0.3% or 17.76 points down at 5,927.43.