One of the greatest catastrophes in the history of Europe arrived almost unnoticed in England in August 1348, in the small port of Weymouth. It was not an invading army, or a messenger with news of war. Most probably it was a small merchant ship of the type that had used the port for centuries. (A)

But on board, carried by fleas on the crew or on the the ship's rats was the bacterium Yersinia pestis, more commonly known as "The Black Death". Once the men and rats had left the ship, millions in Britain were doomed. (B)

To give some idea of the terrible destruction caused by the disease, the number of people it finally killed - some 75 million - is more than the number of people who were killed in all the wars in Europe in the 20th century. And this was at a time when the population of Europe was much lower. In all, the Black Death killed somewhere between one third and one half of the people of Europe. (C)

Yet despite the terrible devastation, many believe that the plague also had a positive effect. Because so many poor people were killed, there were not enough to work the land. The result was that labourers who had been oppressed by the upper classes found that their labour was much in demand, and the feudal system slowly broke down. (D)

The name of the disease which did all this is the Black Death. The name comes from the colour of the swellings which the sufferers developed. (These swellings, or bubos, give the disease its other name, bubonic plague). So great was the devastation in England that more than six hundred years later, it is remembered in folk memory. (E)

Ring a ring of roses, a pocket full of posies, achoo! Achoo! We all fall down.

Could it happen again? We like to think that with modern medical knowledge, and antibiotics, such deadly epidemics are a thing of the past. But a look at modern history is enough to remind us that nature can have some deadly surprises in store. (F)

1. Young children still sing a rhyme about carrying flowers (the smell was believed to hold back the disease), sneezing, and then dropping dead.

2. But an epidemic of 'flu killed millions in 1918, and even today AIDS is a deadly threat that may devastate the populations of third world countries.

3. Also this shortage of manpower caused people to think about the creation of new labour-saving devices. and there was a general interest in technology. The stage was set for the Renaissance which began the modern era.

4. Nevertheless, some doctors thought that the plague was caused by the position of the stars. There was a similar idea about influenza, which comes from the Italian "influence of the stars".

5. The dead were so numerous that is was not possible to bury them properly, not least because those who treated the bodies for burial often caught the plague themselves. Huge holes, called plague pits, were dug, and the bodies thrown into them.

6. The disease was already a raging epidemic in continental Europe. As cities and towns across the continent fell to the plague, there was terror and confusion. Both priests and doctors seemed powerless, and many thought that the end of the world had come.

7. In those days there were very few checks on who went in and out of the country, and as no-one had any ideas how diseases were spread, there was nothing to stop the people of the ship coming into the port.