The flag of the Ministry of Transport.
<a href="//commons.wikimedia.org/wiki/User:Lommes" title="User:Lommes">Lommes</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>, based on the depiction of the flag at <a rel="nofollow" class="external autonumber" href="http://www.crwflags.com/fotw/flags/gb-mtran.html">[1]</a>, incorporating <a href="//commons.wikimedia.org/wiki/File:Imperial_Crown_Heraldry.svg" title="File:Imperial Crown Heraldry.svg">File:Imperial Crown Heraldry.svg</a> by <a href="//commons.wikimedia.org/wiki/User:Sodacan" title="User:Sodacan">User:Sodacan</a>.