I have only a limited knowledge in this area. I had thought especially in the sixties onwards that governments funded their annual deficits by the issue of National Loans which had a maturity date of up to 20 years and had a sinking fund each year to ensure cash available on maturity. I now seem to get the impression that at least some of the National debt "has to be rolled over" which i take means that we have been funding our deficits by short term borrowing which practice had led the banks into all their problems. Maybe i am all wrong!