Thank you very much. I tried both Fran's and user2768's solutions and in both cases it claims not to be able to find the author. The problem lies in the use of the \documentclass{amsart} rather than \documentclass{article}. Is there any way around this?
Here is the code
\documentclass [a4paper, 12pt]{amsart}
\usepackage{graphicx}
\title{Standard Operating Procedures}
\author{Author}
\date{\today}
\begin{document}
\makeatletter
\begin{titlepage}
\begin{center}
\includegraphics[width=0.7\linewidth]{logo_OSP.png}\[4ex
{\huge \bfseries @title }\[2ex]
{\LARGE @author}\[50ex]
{\large @date}
\end{center}
\end{titlepage}
\makeatother
\thispagestyle{empty}
\newpage
\end{document}
and here is the error
This is pdfTeX, Version 3.141592653-2.6-1.40.22 (TeX Live 2021) (preloaded format=pdflatex)
restricted \write18 enabled.
entering extended mode
(./front page.tex
LaTeX2e <2020-10-01> patch level 4
L3 programming layer <2021-02-18>
(/usr/local/texlive/2021/texmf-dist/tex/latex/amscls/amsart.cls
Document Class: amsart 2020/05/29 v2.20.6
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsfonts/umsa.fd)
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsfonts/amsfonts.sty))
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics/graphicx.sty
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics/graphics.sty
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics/trig.sty)
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics-cfg/graphics.cfg)
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics-def/pdftex.def)))
(/usr/local/texlive/2021/texmf-dist/tex/latex/graphics/epsfig.sty)
(/usr/local/texlive/2021/texmf-dist/tex/latex/psfrag/psfrag.sty)
(/usr/local/texlive/2021/texmf-dist/tex/latex/l3backend/l3backend-pdftex.def)
(./front page.aux)
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsfonts/umsa.fd)
(/usr/local/texlive/2021/texmf-dist/tex/latex/amsfonts/umsb.fd)
(/usr/local/texlive/2021/texmf-dist/tex/context/base/mkii/supp-pdf.mkii
[Loading MPS to PDF converter (version 2006.09.02).]
) (/usr/local/texlive/2021/texmf-dist/tex/latex/epstopdf-pkg/epstopdf-base.sty
(/usr/local/texlive/2021/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))
LaTeX Warning: No \author given.
./front page.tex:18: LaTeX Error: There's no line here to end.
See the LaTeX manual or LaTeX Companion for explanation.
Type H for immediate help.
...
l.18 {\LARGE @author}\
[50ex]
?
[0
Non-PDF special ignored!
header=psfrag.pro
{/usr/local/texlive/2021/texmf-var/fonts/map/pdftex/updmap/pdftex.map} <./logo_
OSP.png>] (./front page.aux) )</usr/local/texlive/2021/texmf-dist/fonts/type1/p
ublic/amsfonts/cm/cmbx12.pfb></usr/local/texlive/2021/texmf-dist/fonts/type1/pu
blic/amsfonts/cm/cmr12.pfb>
Output written on "front page.pdf" (1 page, 89386 bytes).
SyncTeX written on "front page.synctex.gz"
Transcript written on "front page.log".
\maketitlehas a predefined layout. To change it you should edit that command. In your case, is better to type the title page as you want. Instead of using\title{}format it using\textbf{},largeor something else. Also, you can use\vspace{??cm}to insert vertical space. – Sigur Jul 26 '13 at 13:51