Several times in the past three or four years I have found myself at the National Archives in Kew (it's a blessed place, with a lake and a heron) looking at old, browning secret files.
These documents have mostly been MI5 and Special Branch reports on Communist activities from the '20s to the early '60s and I have mostly been consulting them for what they said about my parents and their friends who were Party members back in the day.
But these are often, unwittingly, testaments to the social attitudes of the time. By and large, the senior officers in the secret services were upper-middle-class Britons (a fair few knights among them), as were the men and women reporting to them, with a leavening perhaps of petit bourgeois sergeants.
And their unconscious prejudices - or rather those beliefs they held as being normal and uncontestable - are often fascinating. Such as their belief that you could tell from looking, who was and who was not a Jew.
Today, if you go on a BBC or newspaper website to read a story about antisemitism, say, it will be illustrated either by gravestone with a swastika on it, or else a photograph of a bearded, male Jew in full ultra-Orthodox battle-dress.
Philip Green sounds like Alan Sugar who sounds like my dad
Which you could argue is a bit like illustrating a piece on racism with a Zulu warrior or a Masai hunter. There are, of course, some Jews who dress like that, but most don't.
You can see the problem, though. What does a Jew look like? Or, at least, one sufficiently "Jewish-looking" to illustrate a general piece on antisemitism?
Imagine that you just attached a picture of, say, Barbra Streisand or Howard Jacobson (why them? I'll tell you in a moment).
Judging by the files at Kew, this was not a problem until the early 1950s. Special Branch sergeants in plain clothes attending party meetings in the '30s and '40s were able to assess by looks alone that out of, say, 80 people, 30 were Jewish.
Following one of our local comrades around Hampstead and Belsize Park in the early '50s, her "tail" saw her meet a "young Jewish woman" outside a shop.
This woman's clothes were de-scribed, her physical appearance was not. It was assumed by both spy and spymasters that they agreed what a Jewish woman looked like and that the information was useful.
Then, again in the early 50s, the descriptor vanishes. It just disappears. The idea that there is a distinct Jewish physiognomy which is helpful for spies simply peters out. Why?
You can only surmise. Has there been an updating of the handbook Tips for Tails, in which the author points out that there are few reliable ways of distinguishing a Jew per se from any other person?
Or is there a slightly belated recognition of where a racial stereotyping of people can lead you? Both, perhaps.
If you Google "Jewish looking" and hit "images" you will be treated to a page full of pictures of men, almost all dark, many with a beard but - oddly - none of them peyoted and yarmulked. David Baddiel is there, so is Howard Jacobson, so is Bernie Sanders. Further down and more capriciously you will find Prince William and Scarlett Johansson.
The pictures have been posted by websites, many of them on the far right. Indeed, the closer to a big-nose, big-lips, big cigar stereotype, the greater the likelihood that the source is a neo-Nazi one.
On one of these sites, Druid Warrior says he can tell a Jew just by "the nose and the hair". But another poster (Druid Worrier perhaps) is concerned that many European Jews are "entirely white… I know a lot of Jews that could pass as Nordic or Germans".
By the way, try Googling "Jewess" and "images" and you will discover that these are almost entirely the product of Nazis who hate Barbra Streisand.
Well, can you tell a Jew just by the looks? Have you ever said in casual conversation that he or she is or isn't "Jewish looking"? If you have (and I suspect that most of us are guilty) would you really like to put a picture to your assumptions - to paint a painting of a typical Jew?
I imagine I can sometimes tell an old East End Jewish person by the accent and intonation. Philip Green sounds just like Alan Sugar who sounds just like the late Sydney Tafler. And they all sound just like my dad.
I think I can sometimes tell a North London Jewish Princess by her clothes and mannerisms. Other than that, nah. That's why we have Jewdar - because Jewlooks doesn't really work.