A lawyer took a walk through a deep dark wood
A fox saw the lawyer and the lawyer looked good
Where are you going, tired little dude?
Come to my den, and I’ll have some food
It’s terribly kind of you, fox, but no
I’m going to Court with this Bundle-Oh
A Bundle-Oh? What’s a Bundle-Oh?
A Bundle-Oh? Why didn’t you know?
He has terrible jaws and a terrible spine
And if I don’t carry him, I will get fined
His dimensions are wrong, he won’t fit on the shelf
And if he flies at you, well its bad for your health
If he pins you down there’s no hope of escape
You can’t truss him up with a bit of pink tape
His innards are massive, to count them would take ages
Listing what he’d eaten would take pages and pages
So while carrying him is quite bad for my back
It’s better than facing a front on attack
And fox, if you thought, you’d best him in a scrap
Beware, because the Bundle-Oh is foolscap
Away the fox sped
Silly old fox, didn’t you know?
You can’t HAVE a foolscap Bundle-oh
Beware the Bundle-oh my son, the jaws that bite, the claws that catch
suesspiciousminds 
Foolscap?? you’re showing your age, mon vieux..
Although, pertinent to the P’s cordial observations on the size of lever arch files, the following from Wiki gives food for thought in relation to using A4 paper in a foolscap file:
“The slightly larger size of such a binder [i.e. foolscap size] offers greater protection to the edges of the pages [i.e. A4] it contains.