A new challenge for Britain: Its people are growing older much faster than the birthrate is rising and the work force expanding.
It is a situation already being confronted in the United States and in Western Europe - but here, at a time of prolonged economic recession, it adds up to an even sharper economic, social, and political concern for the government.
It is emerging as one of the major background reasons why Prime Minister Margaret Thatcher has ordered controversial new spending cuts that will be a dominant political issue here for her entire second term of office.
Suddenly, Parliament and people are confronting evidence like this:
* The number of people aged 85 and over will double by the end of the century (to almost 1 million) - but the number holding full-time jobs will rise far more slowly (from 30 million to 32 million).
* Retirees already occupy more than half of all British hospital beds, account for a heavy proportion of outpatient care, and are the main users of local government day centers, meals on wheels, and home helpers.
* Financial support for one pensioner was shared by about 31/2 workers in 1979, but government figures show the same support falling on fewer than three workers by 2029 - and that assumes a rising birthrate and economic recovery, neither of which is certain.
* Even conservative estimates show that the cost of state pensions alone is likely to double by about the year 2000, raising the prospect of major tax increases to finance them.
In one way, of course, Britain is facing a challenge bred by success.
The British people are living longer because of better health, housing, food, and other conditions. Britain is still, despite recession and unemployment, a pleasant and stable country in which to live.
In addition, more and more youngsters are spending longer and longer at school and college rather than racing into the work force and earning taxable salaries.
Viewed from another perspective, however, a growing legion of pensioners relying on a shrinking work force at a time when the birthrate and traditional British industries are contracting adds up to a disturbing dilemma.
Mrs. Thatcher said in a recent television appearance that current public spending cuts, which are reducing health care spending among other categories, reflected long-term concerns.
'' . . . By the time people like me are old age pensioners, there are going to be rather more than there are now,'' the prime minister said.
''We are all going to live longer, and more young people are going to want to stay in education longer, and we have to look at the burden on both those ends of the working population. . . . They have to earn the money, (and) they have to feel that they are being left with enough of their own earnings. . . .''
The Tory government found itself ordering spending cuts of 1 percent soon after its massive reelection - and facing charges of ineptitude and lack of foresight.
Health care workers say that cuts already made (as well as others reported to be on the way in the autumn) will hit existing pensioners hardest by reducing plans to expand hospital beds and other care.
The National Federation of Old Age Pensions Associations calls for ''adequate'' pensions and proper health care, rather than more piecemeal aid supplements ''which creates a class of latter-day Oliver Twists always asking for more.''
To the opposition Labour Party, which is looking for every opportunity to criticize the government while still deep in its own internal crises, Mrs. Thatcher is threatening the welfare state itself.
The Labour Party, still recovering from its huge electoral defeat June 9, accuses Mrs. Thatcher of having had a ''secret manifesto'' - cutting the welfare state.
Chief Thatcher spokesman Bernard Ingham replies: ''Bunkum and balderdash. . . . This is a sensible government looking a long way ahead.''