London is making a slow start to the week on a day when the US market will be closed for Presidents' Day. City traders expect the blue-chip index to open around 12 points down from Friday's close. Sausage skins maker Devro produced full-fat results for 2010 with operating margin improving sharply to 16.1% from 12.4%. Profit before tax and exceptional items in 2010 rose 44.4% to £36.3m from £25.1m in 2009. Royal Dutch Shell has agreed to sell most of its stake in nearly all its retail and distribution businesses in Africa to a private equity fund for around $1bn (£616m).Bluetooth chip specialist CSR has unveiled a $680m merger with US peer Zoran accompanied by a $240m share buyback programme.Property firm Great Portland Estates has swapped its freehold interest in 79/89 Oxford Street with a private investor in return for a new 250 year leasehold interest at both 79/89 Oxford Street and the adjoining property, 73/77 Oxford Street.Sector peer Hammerson reported adjusted profit before tax of £144.5m for 2010, up from £130.0m in 2009.