According to E. Bartholomew's "Early Armoured Cars", it was called "Motor Scout" by its creator, Frederick Simms, who is demonstrating its use at Richmond Park in 1899. It featured a Maxim gun and a 1.5 HP engine and was based on a de Dion motor quadricycle design.
Simms also designed a rail-bound armoured vehicle and the road-car "Motor War Scout", which was demonstrated at Crystal Palace in 1902: