It was written by Graham Pratt and is in the DT Here, but the tune is not as Graham wrote it. There is a previous thread here where this is discussed. I have posted a MIDI-TEXT version of the correct tune and also a SONGWRIGHT version with which you can correct the tune on your home copy of DT here.

If anyone wants me to e-mail them a midi file - pm me or e-mail me on dave_bryant@bluecarrots.com with your e-mail address and I'll send yo one.