Bertrand Russell's autobiography is presumably the original source for this anecdote. Here's the event as described in the autobiography (fake paragraphing inserted for clarity). According to the biography, it actually happened some time prior to 1918.
It was decided at Leeds to attempt to form organizations in the various districts of England and Scotland with a view to promoting workers' and soldiers' councils on the Russian model. In London a meeting for this purpose was held at the Brotherhood Church in Southgate Road. Patriotic newspapers distributed leavelts in all the neighbouring public houses (the district is a very poor one) saying that we were in communication with the Germans and signalled to their aeroplanes as to where to drop bombs. This made us somewhat unpopular in the neighbouthood, and a mob presently besieged the church. ...
The mob burst in led by a few officers; all except the officers were more or less drunk. The fiercest were viragos who used wooden boards full of rusty nails. An attempt was made by the officers to induce the women among us to retire first so that they might deal as they thought fit with the pacifist men, whom they supposed to be cowards. ...
Two of the drunken viragos began to attack me with their boards full of nails. While I was wondering how one defended oneself against this type of attack, one of the ladies among us went up to the police and suggested that they should defend me. The police, however, merely shrugged their shoulders. "But he is an eminent philosopher," said the lady, and the police still shrugged. "But he is famous all over the world as a man of learning," she continued. The police remained unmoved. "But he is the brother of an earl," she finally cried. At this the police rushed to my assistance. They were, however, too late to be of any service, and I owe my life to a young woman whom I did not know, who interposed herself between me and the viragos long enough for me to make my escape.
All the elements are in the original: the chivalry, the attacks with random objects, the comical deference to hierarchy. But the anecdote has undergone some well-placed mutations:
Altogether, I must say the later version is more memetically fit. Therefore, that's what actually happened. Another blow for the old primary sources, Jack. How long can they continue to be given their current respect when mutated versions are so much better?
(1) Tue Jan 03 2006 09:03 PST Battle of the Bertrand Russell Anecdotes:
I thought I'd do something useful today, so I'm going to put a new fact on the Internet. There's an anecdote about Bertrand Russell which goes like this:
Around the time when Cold War started, Bertrand Russell was giving a
lecture on politics in England. Being a leftist in a conservative
women's club, he was not received well at all: the ladies came up to
him and started attacking him with whatever they could get their hands
on. The guard, being an English gentleman, did not want to be rough
to the ladies and yet needed to save Russell from them. He said, "But
he is a great mathematician!" The ladies ignored him. The guard said
again, "But he is a great philosopher!" The ladies ignore him again.
In desperation, finally, he said, "But his brother is an earl!" Bert
was saved.