Removing a disk

Perhaps this isn't a much needed feature, but is there a way to remove a disk from the pool without moving data around?

I had 4x 1TB disks in the pool which I've copied to a single 4TB disk.  I want to remove the old 1TB disks from the pool without moving data onto other disks.  It seems that this isn't possible.

Ideally I could just collapse the pool without doing anything to the individual disks but I don't see that either.

Thanks.