In article ,
Tom Gardner wrote:

Somewhere in this house, I have a Ministry of Food booklet from the
1940s which describes the preservation of garden produce ("Dig For
Victory" and all that). It describes the bottling of fruit, and
says that bottling vegetables at home should not be attempted, as
it needs to be done under pressure.

As supporting evidence for that...

"Home Preservation of Fruit and Vegetables" by Fish.& Food,Min.of
Agriculture (Jul 1989) isbn 0112428649, first published in 1929

That's almost certainly an updated version of the same booklet.
Perhaps not even updated very much :-)


Regards,
Nick Maclaren.