Sir, - In April, when the famine in Southern Sudan first attracted the media spotlight, it was estimated that 300,000 people faced food shortages. By early June, all evidence suggested that over half-a-million people were threatened by the famine. Now, at the end of July, two-and-a-half million people are in need of urgent assistance.The world has been watching this famine spread its grip steadily across Southern Sudan. Are we so powerless that nothing more could have been done? - Yours, etc., John O' Shea,Dun Laoghaire,Co Dublin.