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* FTSE falls after 4 straight days of gains
* Energy shares track weaker oil prices
* Prudential shares gain after results
By Atul Prakash
LONDON, Aug 10 (Reuters) - Britain's top equity indexretreated from a 13-month high on Wednesday, with shares inSmith & Nephew falling on a broker downgrade and energyshares losing ground after crude oil prices fell on oversupplyconcerns.
The UK Oil and Gas index fell 1.1 percent, thetop sectoral decliner, after a global supply glut weighed on theenergy market and analysts said that talks of a potentialproducer meeting to discuss propping up prices was unlikely tohave any impact on supplies.
Shares in Royal Dutch Shell, BP and TullowOil fell 1.0 to 2.1 percent, pushing the blue-chip FTSE100 index to trade 0.2 percent lower by 0824 GMT. It hadclimbed to its highest level since June last year following fourstraight sessions of gains.
"Lower crude prices are hurting the oil majors and puttingpressure on the broader market," Jawaid Afsar, senior trader atSecurequity, said.
"Given the recent gains in the FTSE, it would not be toosurprising to see a short-term pullback. We have had a good runpost-Brexit and a breather could prove to be quite healthy."
Among other sharp movers, Smith & Nephew fell 1.2percent after Barclays cut its stance of the stock to "equalweight" from "overweight".
"We believe its transition to higher growth platforms isunderappreciated by the market ... However, with resultscontinuing to disappoint and an upcoming management teamtransition we see a lower probability of upside optionalitycrystallizing within the next year," Barclays analysts said in anote.
However, insurer Prudential rose 3 percent. Althoughthe company reported a fall in first half profits, it said thatit was well placed to capitalise on positive structural trendsand emphasised its ability to deliver both growth and cash.
Randgold Resources advanced 1.8 percent afterPanmure raised its target price for the stock to 6,892 pencefrom 6,750 pence and as gold prices rose more than 1 percent ona weaker dollar.
In the mid-cap sector, G4S surged more than 15percent after the world's largest security firm posted an 8.2percent rise in first-half core earnings, maintained itsdividend and said it was making substantial progress in itsturnaround plan.
Its shares were headed for their best one-day gain in nearly15 years.
($1 = 0.7669 pounds) (Reporting by Atul Prakash; Editing by Keith Weir)
