Finding Out About Francis Williams

I've had this article from the London Review of Books open for several weeks. I don't know how I came across it, so when I finally read it just now, I wasn't sure why I had saved it or what I was in for.

It's an art history mystery about a portrait of a man named Francis Williams, but it's also about 18th century social justice (or lack thereof), plus Halley's Comet. 

And it even includes a coincidence involving Benjamin Lay, one of my favorite figures from the same time period.