But it had happened there

"Most of us," said British Prime Minister Margaret Thatcher, "did not think these kinds of things could happen in our country." That is why Mrs. Thatcher and a good many other people on her side of the political fence in Britain were surprised by the wave of rioting and violence sweeping through its cities.

It also exposes ignorance of history.

The idea that Britain is immune to the violence which can come with periods of severe economic change or from political repression is mythology arising from wishful thinking.

In Britain during the depression years of the late '20s and early '30s there was high unemployment, unrest, some rioting, some police repression, and a general strike which nearly paralyzed the country.

Before that there were many times in British history when troops were called out to put down rioting, dissension, and, indeed, rebellion.

There were two civil wars. King Charles I started the fighting in one of those by raising his standard against the armed forces of the Parliament. That was in 1642. The fighting lasted for six years and ended only when King Charles himself was caught, tried, and beheaded on a scaffold just outside his handsome new dining palace called the Whitehall. That was on Jan. 30, 1649.

The earlier civil war, called the War of the Roses, kept England in turmoil from 1455 to the death of King Richard III on Bosworth Field in 1485. For most of England it meant 30 years of political uncertainty, economic decline, and frequent killings on many a blood- soaked field of battle.

The more important other incidents of rioting and repression were the following.

A "Chartist" movement developed in 1883 out of working-class desire for a share in the political process. It was the beginning of trade unionism. It was broken in 1848 when the Duke of Wellington led regular troops against a march of Chartists intending to enter London.

The Napoleonic wars ended in 1815. For the next four years England seethed with unrest arising out of high unemployment, economic depression, food shortages, and political repression. The climax came on a hot August day (the 16 th) in 1819 when an estimated 60,000 unhappy Manchester workers, wives, and children gathered in St. Peter's field just outside the city. The frightened authorities sent the cavalry to break up the demonstration. Sabers were drawn. Some 500 of the demonstrators were wounded, 11 killed. The event was labeled the Peterloo Massacre and is so recorded to this day in the history books.

Shortly before that the industrial revolution had caused unemployment in the old hand industries, particularly in textiles. Those dispossessed by the new spinning and weaving mills formed groups which sortied at night, masked, to the new factories and destroyed the machinery. They were called Luddites. They were met by police and troops. Many were caught and executed. The phenomenon lasted for three years and peaked in 1813.

The earliest important example of trouble of this kind in Britain was in 1381 . It is called the Peasants' Revolt. Its principal leader was a man named Wat Tyler who apparently enjoyed considerable qualities of leadership. He led a band of peasants infuriated by high taxes and feudal duties against London and actually was able to occupy the city for four days. He was finally caught and executed. But his efforts brought reform laws which abolished "villeinage," the laws which bound a peasant to the lord of the manor.

Add that the Irish, Welsh, and Scots have many times rebelled against English rule and many times been put down by the sword.

July's violence in Britain has several causes. High unemployment in ethnically "impacted" areas is one. Another is shortage of low-rent housing. Another is recent migration into Britain from former colonial countries of peoples not easily integrated into what had traditionally been an all-white population.

Add another seldom mentioned factor. Previous troubles of this kind in Britain have often been eased and even resolved by migration. Britain habitually exported its unemployment to North America, Australia, New Zealand, and South Africa. But since World War II Britain has imported more unemployment than it has exported.

Mrs. Thatcher has a problem on her hands. It is not as surprising as she seems to think. But that will not make t he solution any easier.