On 13 Jul 2021, at 18:47, Fabrice Couvreur <fabrice1.couvreur@gmail.com> wrote:
>
> Hi,
> For my book, the header for each chapter should be like the attached image. I don't know if I am using the best method, but the result looks like what I want. Nevertheless, I am having a problem.
> I don't understand why the first chapter is not numbered while the second is with number 1 etc.
> Thanks.
> Fabrice

You were nearly there. Use:

\unexpanded\def\processheadnumber#1%
   {\getmarking[chapternumber][current]}

—
Bruce Horrocks
Hampshire, UK

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