THIS week was one of the busiest weeks in a long time for the mandarins at the Central Bank. Several times the Bank decided to intervene to buy pounds to push it higher against the deutschmark. Its motivation was to keep a firm exchange rate against the German currency to underpin Ireland's already strong case for participation in the move to a single currency. However, intervening to buy the pound also pushed it higher against sterling, causing some unhappiness among exporters to the British market.