The UK's biggest car dealer Pendragon almost tripled interim pre-tax profit as demand at its aftersales and used car operations steps up a gear.First half used car volume increased by 15.9% over the prior period. Underlying operating margins rose to 2.2% from 1.9% in 2009 as it reduced costs.Revenue rose to £1.8m for the six months to 30 June 2010 from £1.6m the year before while pre-tax profit surged to £13.3m from £4.8m before. Commenting on the results Pendragon said, "Despite challenging economic conditions, the business has performed strongly against the prior year."Used car volumes have improved with used margins returning to a more normalised state. The new car market has recovered in 2009 with stronger recovery in the prestige sector and a more moderate recovery in the volume sector, the group explained.The firm, whose Stratstone dealership sells premium cars such as and Mercedes Benz and Maserati, said the new car market has enjoyed particularly strong growth in the prestige sector.Pendragon said it expects the rest of the year to remain in line with company expectations as it builds on the strong start to 2010.