In your main file, load the geometry package before including the file i10preamble:
\usepackage{geometry}
\include{i10preamble}
and then add the following lines:
\makeatletter
\renewcommand\tableofcontents{%
\if@twocolumn
\@restonecoltrue\onecolumn
\else
\@restonecolfalse
\fi
\newgeometry{textwidth=14cm}
\chapter*{\contentsname
\@mkboth{%
\MakeUppercase\contentsname}{\MakeUppercase\contentsname}}%
\@starttoc{toc}%
\if@restonecol\twocolumn\fi
\restoregeometry
}
\makeatother
The idea is to define a new geometry for the ToC and then to restore the default values.
While I'm not sure why one would want to add a TOC entry for the table of contents, there can be a case where this is wanted: institutions that don't know better than imposing hilarious requirements for theses.
If you load the tocbibind package with
\usepackage{tocbibind}
not only the table of contents will appear automatically, but also the list of figures, the list of tables, the bibliography and the index.
Just in case, it's easy to avoid the TOC in the TOC by adding the nottoc option:
\usepackage[nottoc]{tocbibind}
Why didn't your method work? Because you probably are using a two-sided setup. So the \newpage will simply end the current page (1) and \addcontentsline{toc}{chapter}{Table of contents} appears at page 2, but \tableofcontents starts on the next right hand page, which is number 3.
The "manual" method should be
\cleardoublepage
\addcontentsline{toc}{chapter}{\contentsname}
\tableofcontents
but a higher level method is preferable; for instance, tocbibind works correctly also with hyperref, while the manual method requires another intervention.
Note that with the memoir class the declaration
\tableofcontents
adds the TOC in the TOC; the \tableofcontents* variant doesn't.
Best Answer
From your question is not very clear (to me), how your document (article?) should look:
\tableofcontentsis in one column, the following rest of document in standardtwocolum:\tableofcontentsis reserved whole first page in one column layout and the following rest of pages intwocolumlayout:For testing above cases I need from you a Minimal Working Example (MWE). See, which of above cases you actually like to have.