LONDON -- The institution of marriage has been taking some hard knocks lately. It is not just that cohabitation -- living together without the marriage commitment -- is now increasingly popular. Nor yet that, as is widely known, one in four British marriages end in divorce. (In the United States, the figure is higher, in Japan considerably lower; but who knows what is to come?)

More serious still is the trend toward the removal of the whole concept of marriage from public law and from the administrative structure of the state. The issue has been highlighted in Britain by the recent case of a young woman whose partner, a soldier, was killed while on active service in Sierra Leone. They were not married, but she had born him a child. She therefore claimed a full soldier's widow's pension to help bring up the child. Not possible, say the high officials in the Ministry of Defense.

Some minor help can be offered in this particular case, but full compensation and an army pension are not available to partners, however long-standing -- only to married wives. The case has now gone to the courts to decide.