3 phase distribution transformer question

[ghub005-at-xtra.co.nz (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

I have been offered a three phase 15kVA, 11kV, 240/415 volt 
distribution transformer - free if picked up.

What would happen if this unit was run on single phase 240V? Apart 
from derating the output voltage by sqrt(3), can a three phase core 
cope without all of the separate magnetising currents?

I would appreciate any information or hearing about the experiences 
that others have had with single phase operation of three phase 
transformers.

Safe coiling,

Gavin Hubbard

P.S. Mark - this transformer is intended for you ;-) Needs to be 
picked up from the Waikato region though (Hamilton?)