Grosvenor Square 1968 has become a common piece of historical shorthand (Feature, Socialist Review, May 2008).
There was a demonstration against the Vietnam War in March 1968 in London. It did not go to the US embassy. The battle of Grosvenor Square, when the police mounted full scale cavalry charges, was in October 1967.
The March 1968 effort was much larger but much more passive. Tariq Ali led it off to Hyde Park, and only the ultra-lefts (yes, I was one) went to Grosvenor Square, where we were totally outnumbered by the police (who didn't lose it this time). Apparently, at the end, they all sang Auld Lang Syne together (no, I didn't). There was none of that in 1967.
This is not only important for my personal history, but because it illustrates that May 1968 was the highest point of what was a much longer, multi-faceted, interacting international process.
The insistence on the importance of the total international process from the US civil rights movement of the early 1960s to the industrial struggles of the early 1970s, is the strength of Chris Harman's book on 1968, The Fire Last Time. The only weakness is that our heroic, near insurrectionary, struggles in the then new University of Essex barely get a mention.
The 17 March 1968 demonstration certainly was not a peaceful affair, as the classic Granada TV documentary showed. The October 1967 one (of which I was one of the organisers) was the first to show the militancy building up. But the March one was three or four times larger. There was no doubt in anyone's minds that we intended to try to battle our way to the embassy. The demonstration that went to Hyde Park was the October 1968 one. We had learnt the hard way that the police could make the US embassy impregnable and so instead took over a vast swathe of London's streets.