yarnsplicer - thanks for bringing this subject up. I hope someone's memory is eventually jogged about Germany as it certainly seems very possible that your father was telling it exactly how it was. You are not alone in leaving it too late to find out more about the stories that were handed down to you - there are so many (less exciting but still interesting to me) things I wish I had asked my father more about and we will be in good company there, I'm sure.
On a technical note - does anyone know roughly what quantity of ball bearings they were able to carry in a Mossie? I know they're small things individually but I would have imagined the British war effort would have needed some fairly serious amounts of them. Where/how did the Americans get theirs?
If the Americans had their own domestic supply, which presumably would have also been available to the UK, then it was definitely an issue of depriving the Germans of having them rather than British need as such.
In the (almost unthinkable) event of a repeat performance in this modern globalised world of ours this sort of issue would probably bring most countries to their knees quicker than actual hostilities as so much essential production and know how is now centralised in isolated specialist centres in much the way as the Swedes had the near monopoly on European ball bearings back then.