Setting a default font in Keynote

Hi there,

I am trying to set a default font and font size in Keynote such that when I add a new text box the font is not 'Helvetica'.

A Google search only seems to explain how to change the font of a text selection but not how to have the font you want in place when you create a new text box, such as I use as a title or description of a graphic on a slide.

In the example below a new text box has a default font of Helvetica Neue and I would like Arial Narrow. The only way around this so far is for me to copy and past text boxes from other slides but that is not always convenient.

Thank you.