Changes made by Social Security (Widow's Benefit and Retirement Pensions) 1979
S.I. 1979/642
Made to Social Security (Miscellaneous Amendments and Transitional Provisions) 1975
1 change. All changes made by Social Security (Widow's Benefit and Retirement Pensions) 1979
From legislation.gov.uk's record of changes, the official one: see it there.