Changes to Social Security (Widow's Benefit and Retirement Pensions) 1979
S.I. 1979/642
Made by Civil Partnership (Pensions, Social Security and Child Support) (Consequential, etc. Provisions) 2005
32 changes. All changes to Social Security (Widow's Benefit and Retirement Pensions) 1979
From legislation.gov.uk's record of changes, the official one: see it there.