electric brake wiring size

I am about to fit an electric brake controller (Hayman Reese) to the Landcruiser. Upon examination of the vehicle wiring harness (factory fitted) there is the blue wire already connected to the correct pin at the trailer plug.

However it is the typical thin guage wire that comes complete in the 7 core flex........where the other end is connected to I have no idea as I havent looked....not really relevant anyway

Instructions with the controller do not suggest the wire size from the controller to the trailer plug nor does it give an expected amp draw for the electric brakes........I am assuming that the existing trailer wiring harness is too smaller a dia and that thereforeI will be running a dedicated blue wire for the controller to the trailer plug (and severing the existing one)

BUT can anyone tell me the expected amp draw of the brakes on the caravan and therefore allow me to do the job with the correct size cable?

Thanks