"Dragons teeth" anti-tank obstacles by the <a href="//commons.wikimedia.org/w/index.php?title=River_Wey&amp;action=edit&amp;redlink=1" class="new" title="River Wey (page does not exist)">River Wey</a> near Guildford.  Part of the GHQ Stop Line in World War 2 in anticipation of a German invasion.
<a href="//commons.wikimedia.org/wiki/User:Murgatroyd49" title="User:Murgatroyd49">Murgatroyd49</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>