Trevor,
You're quite right about swede (rutabaga to those of us in the US) - it's the answer to the question "What the %)#%$*! could be worse than a turnip?!?"
Spaw - I know the old "turnips for potatoes" bait-and-switch from my growing up, too. (I suspect that those who insist "you can't tell the difference between them" are among those same poor taste-bud impaired folk who claim that carob "tastes just like chocolate"...and if carob were a vegetable, it would be on my heave list, too.)