Changing font of "Table of Contents"

[Nick Payne]

I'm putting together a book of pieces, and using a particular font for
headers, footers, titles, subtitles, etc. The one place where I haven't
figured out how to get that font used is for the header text for the table
of contents that Lilypond creates. Each tocItem has the font I want by using
\override #'(font-name etc, but how do I change the font for the actual text
"Table of Contents" that Lilypond inserts corresponding to the \markuplines
\table-of-contents in the ly source.

I tried using 

\markuplines { 
        \override #'(font-name . "SpectrumMT SC")
        \table-of-contents
}

In the same way as inside \markup blocks, but that doesn't parse correctly
and gives errors.

Nick