Table socket Trident

I have a 2009 Trident. 

Does anyone know how the metal table leg socket is secured into the hole in the rear floor? In the bottom centre of the socket there is what could be the head of a captive bolt, so I wondered if there is a nut underneath the van behind the plastic undertray that has to be accessed.

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It should be like the one shown at the link above. Screwed from above around the perimeter.

Thanks for the reply. Mine does not have the screw holes. No visible signs at all as to how it is secured, apart from the possible bolt head in the bottom.