This is a service held at night and continuing till after midnight. Such services had a precedent in the Vigils of the early Church. John Wesley encountered them among the Moravians, who held them on New Year's Eve. Hearing that they had started spontaneously at Kingswood, he encouraged them monthly on the Friday night nearest the full moon, but this was gradually replaced by the Moravian practice. Charles Wesley's Hymns for the Watchnight (1750) was reprinted a number of times. The practice spread to other denominations, but in our own day has been largely replaced by the Christmas Eve Communion Service.
'About this time, I was informed that several persons in Kingswood frequently met together at the school; and, when they could spare the time, spent the greater part of the night in prayer, and praise, and thanksgiving. Some advised me to put an end to this; but, upon weighing the thing thoroughly, and comparing it with the practice of the ancient Christians, I could see no cause to forbid it. Rather, I believed it might be made of more general use. So I sent them word, I designed to watch with them on the Friday nearest the full moon, that we might have light thither and back again. I gave public notice of this the Sunday before, and, withal, that I intended to preach; desiring that they, and they only, would meet me there, who could do it without prejudice to their business or families. On Friday abundance of people came. I began preaching between eight and nine; and we continued till a little beyond the noon of night, singing, praying, and praising God.
'This we have continued to do once a month ever since, in Bristol, London, and Newcastle, as well as Kingswood; and exceeding great are the blessings we have found therein…'
John Wesley, A Plain Account of the People Called Methodists (1748)
John Wesley's Journal:
April 1742: 'We had the first watch-night in London. We commonly chose for this solemn service the Friday night nearest the full moon, either before or after, that those of the congregation who live at a distance may have light to their several homes. The service begins at half an hour past eight, and continues till a little after midnight. We have often found a peculiar blessing at these seasons. There is generally a deep awe upon the congregation, perhaps in some measure owing to thwe silence of the night…'
August 1750: 'We had now the first watch-night which had been in Cornwall; and "great was the Holy One of Israel in the midst of us." '