Lu, we remember events this long ago by what else we were doing at the time. I was cold and wet on that little boat in France looking at the colour pictures of that amazing aeroplane, so I think it must have been July or August '67 or '68? I think one of the engines flew off sometime around then too!
Don't worry about mixing up the memories- when you get of 'more mature years', you have so many of them in the barrel that they get intertwined with each other! Just no separating 'em!