Art wrote:
"The Physics World states that displacement current does not exist with
respect to radiation---."

Who and where?

Be reasonable. Free space is normally nonconductive. It is a good
insulator or dielectric. Light is by all accounts an electrromagnetic
radiation. We readily see light from sources throughout space.

Michael Faraday (1791- 1867) wrote:
E = F/Q where E & F are parallel vectors. E = the electric field
strength in force per unit charge and F is measured in newtons per
coulomb.

Electric charges` force on each other are readily measured. Likewise,
magnetic forces` influence on each other and upon electric charges are
readily measured.

Radio waves as Terman says:
"---travel with the speed of light and consist of magnetic and
electrostatic fields at right angles to each other and to the direction
of travel."

Electrostatic does not mean stationary.

There are no conductors in space suited to support an electric current
for wave propagation, therefore it is the invisible but readily
measurable electric and magnetic fields which invoke action at great
distances.

Best regards, Richard Harrison, KB5WZI