Overlapping Entries on Contents Page

Question

This related to this question:

How to merge several tex files so that they have one table of contents/List of tables & figures

I have been trying to get the solution by Jean Mentz to work, it's nearly there but I can't seem to get the table of contents to work?

I've tried it as:

\addtocontents{toc}{Chapter One}
\input{Introduction.tex}

which gives the contents page below with overlapping entries on the first line. Note that Chapter One does not appear anywhere apart from the table of contents.

Doing it as

\chapter{Chapter One}
\input{Introduction.tex}

Means that only abstract appears on the contents page and chapter one just appears as regular text before abstract in the document. It almost seems like the chapter command is not being recognized?

\documentclass{article}
\usepackage{fancyvrb}
\DefineVerbatimEnvironment{code}{Verbatim}{fontsize=\small}
\DefineVerbatimEnvironment{example}{Verbatim}{fontsize=\small}
\usepackage{natbib}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{bm}
\usepackage{grffile}
\usepackage{graphicx}
\usepackage{epstopdf}
\usepackage{booktabs}
\usepackage{siunitx}
\usepackage{longtable}
\usepackage{graphicx}
\usepackage{url}
\usepackage{graphics}
\usepackage{titlesec}
\def\UrlBreaks{\do\/\do-}
\usepackage[%
 font=small,
 labelfont=bf,
 figurewithin=section,
 tablewithin=section,
 tableposition=top
]{caption}
 \numberwithin{equation}{section}

\makeatletter
\def\env@matrix{\hskip -\arraycolsep
 \let\@ifnextchar\new@ifnextchar
 \array{*\c@MaxMatrixCols l}}
\makeatother


\begin{document}
\input{title.tex}
\tableofcontents
\clearpage
\addtocontents{toc}{Chapter One}\input{Introduction.tex}
\end{document}

Answer 1

Does this do what you want? You might wish to adjust the spacing and font for the chapter title but this shows you how to do that. This puts the chapter number on the same line as the title of the chapter. It also sets the value of \chaptername empty which avoids getting 'Chapter 1 ...' in headers even though the first chapter is just '1 ...' in the text.

\documentclass{book}
\usepackage{fancyvrb}
\DefineVerbatimEnvironment{code}{Verbatim}{fontsize=\small}
\DefineVerbatimEnvironment{example}{Verbatim}{fontsize=\small}
\usepackage{natbib}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{bm}
\usepackage{grffile}
\usepackage{graphicx}% loads graphics - no need for both; no need for epstopdf either; or to load graphicx again later on!
\usepackage{url}
\usepackage{titlesec}
\def\UrlBreaks{\do\/\do-}
\usepackage{booktabs}
\usepackage{longtable}
\usepackage{siunitx}
\usepackage[%
 font=small,
 labelfont=bf,
 figurewithin=section,
 tablewithin=section,
 tableposition=top
]{caption}
 \numberwithin{equation}{section}

\makeatletter
\def\env@matrix{\hskip -\arraycolsep
 \let\@ifnextchar\new@ifnextchar
 \array{*\c@MaxMatrixCols l}}
\makeatother

\titleformat{\chapter}[hang]{\LARGE\bfseries}{\thechapter}{.5em}{}
\renewcommand{\chaptername}{}

\usepackage{filecontents}% only so I can include the 'separate' chapters here for convenience (LaTeX writes new files with the given names on compilation which are then \input below)
\begin{filecontents}{title.tex}
    Great title
\end{filecontents}
\begin{filecontents}{intro.tex}
    \kant[1]
\end{filecontents}
\begin{filecontents}{ch1.tex}
    \kant[2-4]
  \end{document}
\end{filecontents}
\begin{filecontents}{ch2.tex}
    \kant[5-9]
\end{filecontents}
\usepackage{kantlipsum}% only to provide filler text for the example

\begin{document}
\input{title}
\tableofcontents
\chapter{Introduction}
\input{intro}
\chapter{Next}
\input{ch1}
\chapter{Another}
\input{ch2}
\end{document}