What's the earthing system if the main earth comes from under the floor with the main incoming cables?

[Mizunoid]

In my house, the mains supply comes in as two cables, into the service head. The main earth comes from under the floor along with them and straight into the consumer unit.

The unit is then bonded back to the steel outer sheathing of the two incomers.

What type of system is this?

 

[Murdoch]

Sounds like TT

 

[SPECIAL LOCATION]

In my house, the mains supply comes in as two cables, into the service head. The main earth comes from under the floor along with them and straight into the consumer unit.

The unit is then bonded back to the steel outer sheathing of the two incomers.

What type of system is this?

Are you sure what you think is the earth conductor, isn't actually a bonding conductor..?
What earth loop impedance to you get at the CU?