I dont know about the Daily Mirror 5 years ago, but I remember discussing this with a friend of mine about 2 or 3 months back, as we had both caught a little snippet about it on the news a few days before. He was surprised, as he said he had previously thought it had been paid off as something of a lump sum in the 70's (not that a large repayment in the 70's seemed that likely to me).