This has been a very enjoyable exercise. Leaving aside unkind remarks about Liverpool, police, and motor vehicles, I can i.d. the vehicle. At first I thought the pic must have something to do with the Liverpool police strikes, but they were in 1918 & 19. It turns out to be rather the opposite - police during the workers' general strike in Liverpool.
Courtesy of Armored Cars in WWI, it's a Hallford lorry, with wooden protection for police officers. Impressive pictures here
Leading from that, it seems that Hallford, of which I hadn't heard before, produced both lorries and buses very similar to the B-Type, in Dartford. Details here:
And there's a Landships connection. Not only were Hallford trucks used on the Western and Home Fronts during the War, but they were designed by Walter Gordon Wilson.
Google "hallford bus lorry" & images; the results are very pleasing.
-- Edited by James H on Friday 2nd of August 2013 04:26:46 PM
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"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
If memory serves, I think the list of vehicle plans on the old Landships site had a 3-view of the truck version of the Hallford. If James hadn't already identified it as such, Hallford would have been my suggestion, as the shape of the engine cowl (or bonnet, or hood) is distinctive and I came across the truck perhaps last year.