Because now especially the country demands tremendus efforts on the part of everyone to save every £ they can. Because I feel I am helping my sons at the war by saving every £ I can scrape together. As any business man will tell you, the good rate of interest, the full trustee security, and the regular payments of interest make these an ideal investment. 328 WHY WE BUY 3% DEFENCE BONDS 3% DEFENCE BONDS. Can be bought for cash in units of £5 from any Bank, Stockbroker, Post Office or Trustee Savings Bank, or by instalments with National Savings Stamps (6d.