Oil giant Tullow tanked on Tuesday after revealing that its Okure-1 exploration well offshore Ghana had encountered 'low net to gross oil bearing reservoir in a secondary objective'. The markets seemed to shrug off its other announcement that it plans to buy Norwegian exploration group Spring Energy for $372m and dispose of its non-core gas assets in the North Sea. That as investors seem to be marking down the premium assigned to the shares for its exploration prowess. Nevertheless, several brokers have come out in defence of the company. Costa and Premier Inn owner Whitbread topped the risers following an in-line third-quarter trading update, in which it revealed that total sales were up 14.4% year-on-year. Investors didn't seem to mind that like-for-like sales growth had slowed to 3.3% from 4.3% in the first half.Polymetal International was also a strong performer after saying that it has entered into a definitive agreement with AIM-listed Ovoca Gold to acquire the Russian legal entity Olymp, which holds the mining and exploration license for the Olcha gold-silver deposit.Mining group BHP Billiton rose after Nomura named it as its preferred name in the global metals and mining industry. Sector peer ENRC however dropped into the red after Citigroup downgraded its rating on the stock to 'sell'.HSBC was higher after reaching an agreement with US authorities in relation to investigations regarding inadequate compliance with anti-money laundering and sanctions laws. HSBC will make payments totalling $1.921bn and take further action to strengthen its compliance policies and procedures. Johnnie Walker, Smirnoff and Guinness owner Diageo was in the red after saying that it has called off talks to buy tequila giant Jose Cuervo after being unable to "agree a transaction".ENRC was off the pace after analysts at Citi downgraded their view on the shares to sell from neutral. They expect that the company will be in breach of its banking covenants in the first half which set out that it ought not to have a level of net debt of more than three times earnings before interest, taxes, depreciation and amortization. FTSE 100 - RisersWhitbread (WTB) 2,506.00p +3.21%Polymetal International (POLY) 1,117.00p +2.76%Evraz (EVR) 251.50p +2.15%Pennon Group (PNN) 618.00p +1.81%CRH (CRH) 1,176.00p +1.64%BHP Billiton (BLT) 2,053.00p +1.53%Meggitt (MGGT) 393.00p +1.50%Tesco (TSCO) 340.60p +1.38%United Utilities Group (UU.) 694.50p +1.31%Aviva (AV.) 364.30p +1.28%FTSE 100 - FallersTullow Oil (TLW) 1,178.00p -6.21%Eurasian Natural Resources Corp. (ENRC) 267.00p -3.33%Burberry Group (BRBY) 1,294.00p -1.67%Rolls-Royce Holdings (RR.) 877.00p -1.63%IMI (IMI) 1,078.00p -1.28%Diageo (DGE) 1,864.00p -1.19%Tate & Lyle (TATE) 762.00p -0.91%Petrofac Ltd. (PFC) 1,691.00p -0.88%BG Group (BG.) 1,067.00p -0.79%Fresnillo (FRES) 1,947.00p -0.71%BC