Betfair topped the risers after analysts at Morgan Stanley raised their price target on the stock from 1550p to 2030p, in a research note e-mailed to clients. "The fourth quarter saw strong revenue growth of 20%, marking the fourth consecutive quarter of 20%+ growth. This is despite tough sports results in the period."Some observers warned that bookmakers could lose up to £50m on Tuesday, as the Cheltenham Festival gets underway. Willie Mullin, the most successful Irish trainer in the history of the festival, will field all four favourites in the top tier races on the opening day of the festival.N Brown was trading lower on an uncertain run-up to its fourth quarter and full year trading update on Wednesday. N+1 Singer's Alex Hardwicke said: "If growth is at the low end in the fourth quarter, the shares could drift back a bit, which would be my bet."St Modwen Properties was trading lower after a downgrade from analysts at JPMorgan Chase & Co. The broker moved its rating to 'neutral' from 'overweight' in a report issued to clients.Gold miners Centamin and Polymetal were down despite a slight rebound in gold prices.