Large 5 inch gauge battery-electric locomotive, I'm reliably informed by those much better read on these new-fangled devices that it's a Class 31. Fibreglass body on steel chassis, remote controller for motor.
Sam spent yesterday afternoon driving this, it's a powerful thing with two motors per bogie and plenty of adhesive weight - there was even juice left in the batteries at the end of the day.
Length 57 inches
Weight approx 140 pounds with batteries