The answer is, of course, it was the Roman Catholic Church. All the connections to Samhain were made up by Victorians and similar wallies. Samhain could be a day, a feast, a month, or a state of mind for all we know. And, as far as we're aware, druids never carved pumpkins.
Still, it was a fine night. In keeping with what is long tradition, many people dressed up as the scariest of all monsters - Russell Brand - although I could have done without Burton Dasset's "Brand" costume being a mask and a pair of white Y-Fronts. The sparks from the Wicker Person flew off and burned down a haystack. And Summer's End was appropriately celebrated.
Happy All Saints' Day. The Little Sisters of the Holy Herring, our enclosed order of penguins, are about to celebrate Vespers. Whatever that is.
Probably invented by the Druids like everything else.