According to a trucker on the rajo.
They take an axle out and use the space for an extra large fuel tank.
This enables them to spend a week or more doing runs around the UK before going back to their base with a full payload and filling up with cheap fuel, before returning to the UK with another full payload and a full tank of fuel.
You surely didn't believe that all those Lithuanian and Latvian etc trucks on the UK 's motorways were competing on a totally fair and equitable basis.
Derek