There is a section on the History of Guy Buses on the History page: Link to History

Guy made buses from an early period in the firm’s history; first of all with buses on Truck chassis, before special designs of chassis were developed. The Guy Arab became, perhaps the most famous with many bus companies buying examples of the type. Arab’s were also very popular in other parts of the world, notably in Hong Kong.

In the 1930’s when the first Arab was made, only a few were sold – barely 60 units , and it could not be said it was an immediate success. There were many competitors from other bus manufacturers, typically Leyland Motors. The turning point came during the second World War, when most factories were turned over to war production, and companies could not make new buses for sale. This changed because the Ministry of Supply recognised that buses were vital to get people to work, and many had been destroyed, or were worn out. The Ministry therefore allowed Leyland an Guy to make a utilitarian bus for sale to operators. The Arab was made in this form and sold to many operators throughout the UK. Leyland could not supply buses in the event because they became more heavily involved in war materials, and so Guy had the market to themselves. This proved to be a very good thing as many operators who had not tried Guy buses before were exposed to them. The Arab design was simple and reliable, and later on, many companies came to use Guy buses. Between 1941 and 1945, 2000 Arab chassis were delivered.