n></h2>
<p>British Morris and MG engines from 1923 to 1955 were built using metric threads but with bolt heads and nuts dimensioned for Whitworth spanners and sockets.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span>[</span>6<span>]</span></a></sup> The background for this was that the engines were produced using machine tools of a previously French-owned company that was set up for metric production; for the average British motorist to be able to service his car, the bolt heads had to fi