Flex your muscles compostpope.
I find that large brassicas can sometimes be snapped off, or moved almost 180 degrees to snap the main roots, leaving soil mostly undisturbed, or I use my sharp copper spade to chop just below stem level in the first layer of soil, again as shallow as possible, so most roots remain in the ground.
I hope you trod the loosened soil down again, its good to dance!