As west lakes above notes our Earth (ie yellow and green) in domestic wiring in the uk is used for fault protection.
But it is not the same as SOIL earth. The wording "Earth" has historic reasons mostly... the UK uses a PME system (Protective Multiple Earths) with only 2 conductors entering each house. These are live and neutral. As noted by other posters the neutral is connected to Earth (soil) at the transformer and likely several other soil earth bonds along the way. In the UK each property does not have a local earth stake that ties the neutral to soil, but here in the US we do. However the UK Earth wire (yellow/green) does the same job as the green wire here in the US - it ensures there is a second uninterrupted return path for any current that finds it way onto any metal parts of an appliance back to the neutral terminal in the fuse/breaker box, to ensure the breaker trips.
FYI - as an ex-pat living in the US, I still prefer the UK system with local fuses in each supply plug. It is infinitely more preferable to have the local fuse blow, than the whole circuit... especially if that happens to be in the lighting circuit, after dark, and you can't remember where the flashlight (torch) is!
- GY