Jim, I'm still puzzled. Front National wasn't founded until 1972, by which time The Singers' Club had found a home in the Union Tavern. So the said convention has to have been earlier that.
It could have been some earlier incarnation of Front National of course, since Le Pen was involved with nazi politics and concomitant thuggery long before he tried to make a bid for "respectability" in the form of FN.
To complicate matters, Marine Le Pen wasn't born until 1968 so, if I've got the chronology roughly about right, she would have been no older than two at the time.
That thought of course would set any fascist claiming the incident as proof of 'the master race'. But I'm wondering whether it might have been some other female member of the infamous Le Pen clan?