Why "KT" and not "KB" ?

[Ellen van Neck <100411.2450@compuserve.com>]

It is in the FAQ as well. 
I'll quote:
(....) Kate's first appearance in the public was a little tour through a few
London pubs together with the so called KT (read: Katie) Bush Band.
All of Kate's albums have the KT (originally Knights Templar) symbol
hidden somewhere either on the cover or on the vinyl itself (...)
The KT initials can also be seen in the "Army Dreamers" video.
The release of the This Woman's Work boxed set there appeared a new
version of the KT symbol that includes the biological symbol for woman: 
_O_
   | <
unquote.

Ellen.