London is set for a boozy, cheery start with trading updates from brewers SABMIller and Marston's occupying attention in the early going.City traders expect the top-shares index to open around 34 points firmer at 5,958.National Grid saw pre-tax profit rise by 25% in the year to the end of March, on the back of continued strong UK returns. The dividend has been increased to 36.37p from 33.68p the year before. Lager brewer SABMiller's group revenue rose 7% to $28,311m in the 12 months to the end of March, from $26,350m the year before. Underlying profit before tax rose 18% to $4,491m from $3,803m the previous year.Food sales continue to drive growth at brewing and pubs group Marston's, though drinkers are putting their hands in their pockets more often, too. Revenue in the 26 weeks to April 2nd rose to £317.9m from £309.2m at the interim stage last year. Profit before tax and exceptional items advanced to £29.2m from £27.8m the year before.Quality and safety services provider Intertek has seen organic revenue grow by 8% in the year so far, as the firm was able to offset a slower-than-expected performance in its Consumer Goods division. The group anticipates achieving organic revenue growth in the high single digit range for the full year.---jh