Mk3 Mondeo rear seat base

[spaceship]

Strange question but does anyone know how this is secured to the car?

Had a look at one this morning and the rear seat base was loose and rattling around. When I checked to find out what the rattle was it appeared that the seat base wasn't secured to the car and lifted out. The loop on the seat base was there, as was a space in the car for it to go into but it didn't lock or secure in place. Any ideas?

Cheers.