The Europeans of the medieval times were brought together by annual festivals, particularly those which were religious in nature. The main feasts of the Christian year were celebrated throughout the Christendom but different areas also honoured different saints. Such celebrations attracted crowds also from the surrounding areas, and large gatherings of people naturally attracted a certain amount of trade. Festivals and trade went hand in hand in England both before and after the Conquest, even though there was no formal recognition of this. Because Saints' Day fairs took place only once a year, bringing together people and money alike, they were important occasions for entertainment and commerce alike. One of the purposes of such a fair was the sale of livestock, both for farmwork and butchers' meat.
Rather than trading on the day of the feast itself, people got together to buy and sell products on the day before, this was known as the wake or vigil. Evidence of this is provided by the Bolton Priory which claimed in the late 13th century that the assembly at Embsay in Yorkshire wasn't a fair but "a certain gathering of men which is called a wake" (Britnell, p.15). Such a statement implies that the abbot of the priory knew people would assemble on the eve of, rather than on the day of their saint's feast.
In 1212 the abbot of Alsingdon claimed that he didn't hold a fair at Sallingford in Berkshire but only a wake, thus implying that he didn't need a permission to hold the event. After all, he most likely received no profit from it. Informal occasions such like these, half for business, half for pleasure, were tolerated well into the 13th century, perhaps beyond that. However, larger fairs, such as the annual fairs which began to take the place of the one-day-long informal wakes, continued until at least a day or two after the saint's festival. For example, the bishop of Winchester was granted a charter which extended the St Giles fait by six days.
Britnell Richard H., The Commercialisation of English Society 1000-1500. Manchester University Press, 1996, Glasgow.
Pounds N.J., An Economic History of Medieval Europe. Longman, 1994, Malaysia.