The majority of people that report having received / witnessed the slipper nearly always refer to size 11 or 12. The average shoe size for a man is between 9-10.5 a slightly larger size range, than back in the 50/70s.
So my question – was this an erroneous belief , the famous slipper looked larger in size to a child than it actually was, exaggeration, or if correct, where did all these large slippers materialise, most slippers were well worn and not all donating PE staff were large hunky specimens,