Born in Devon in 1750, Joanna Southcott declared in 1792 that she was the woman spoken of in Revelation chapter 12, the woman driven into the wilderness. She began to prophesy, proclaiming the imminent return of Jesus, and sold sealed parchments bearing her sayings to the thousands of faithful she gathered around her.
After some years of living like a princess in Exeter, she came to London in 1802, where she continued to make money and trouble in roughly equal measure. However, the city gradually grew bored of her, and it became clear that drastic measures would be needed.
In February, 1814, Joanna confided in a friend that the previous October, she had felt "a powerful visitation working on my body" - and that she was now pregnant, at the age of 64.
With the Messiah.
In fact, she had dropsy, which duly killed her in December 1814. Her followers insist that the miraculous child, known as Shiloh, had been born the day before she expired, but in spirit form.
Her main legacy was a mysterious box supposedly containing prophecies of particularly momentous import, which was to be opened only in time of dire national crisis and in the presence of 24 bishops of the Church of England. In 1927, ghost hunter Harry Price opened what he claimed was the Box in the presence of a couple of minor clergy, and discovered that it contained a few mildly pornographic novels. However, Southcottians maintain that this was not the Box, and given Price's reputation, they may have had a point.
The rump of her following, the Panacea Society, persisted until fairly recently, and may still be going for all I know. They used to regularly place ads in the press asking for the requisite number of bishops to assemble to open the Box, to no avail. But I haven't seen one in quite some time.
There's a picture of her actual gravestone here.
(The opening lines of the first extract from Southcott's prophecies, here obscured by foliage, read:
"While all through thy wondrous days,
Heaven and Earth enraptur'd gaz'd...")