Thanks Martin

I have started my \legendcontent definition thus...

code tex-map 

  \legendcontent={%

  \hsize=\legendwidth

  \color[0 0 0]\the\legendtextcolor

  \ifnortharrow\vbox to 0pt{\line{\hfil\northarrow}\vss}\fi

 % original code commented out

 %  \edef\tmp{\the\cavename} \ifx\tmp\empty \else

 %    {\the\legendtextheadersize\the\cavename}\vskip1cm

 %  \fi

  \edef\tmp{\the\cavename} \ifx\tmp\empty{\the\legendtextheadersize{Caves of the Flora Area}}\vskip1cm \else

     {\the\legendtextheadersize\the\cavename}\vskip1cm

  \fi

  % ... original code continues to end

And it behaves precisely as per my original attempt.

No errors, but also no map title if Therion is not able to identify a unique title.

With multiple maps selected in my thconfig th_texts.tex gives...

\cavename={\mainfont{}}

With one map selected in my thconfig th_texts.tex gives...

\cavename={\thfb\char70 \char108 \char111 \char114 \char97 \ \char67 \char97 char118 \char101 \char115 \ \char80 \char108 \char97 \char110 \mainfont{}}

So I infer that \cavename is indeed empty when there is no unique map title, but the customised \ifx test is not working.  Do I have the ifx syntax correct? (Martins example was split by a line feed inserted by the mail application so I am not sure)

Do we have to dig deeper to find a solution?

I notice the output produced has the appearance of having \vskip1cm applied regardless of the original \ifx test being true or false, but the ‘true’ result code has no \vskip1cm.  Maybe this is a clue? Is there yet another definition that is overriding this code?

Thanks

Bruce