Sir Paul McCartney is struggling to come to terms with the collapse of his marriage to Heather Mills, and is at his lowest ebb since first wife LINDA died eight years ago (98). The former beatle has been putting on a brave face since last month's (MAY06) announcement of his separation from the former model - for the sake of their two-year-old daughter BEATRICE. Business partner Mark Featherstone-witty, who his chief executive of MCCartney's Liverpool Institute For Performing Arts, says, "It is the lowest I have seen him since Linda died. "They are totally different circumstances, but he looked extremely tired and worn out by the whole situation (when I saw him). He is going through a bad patch. "He is still speaking to Heather, they have a child together and have to work that out."