British army trucks of the 30s: identification

[Konstantin Chernov]

British military vehicles from the album "All vehicles, artillery pieces, guns, equipment & apparatus" https://www.flickr.com/photos/394117...7631983929201/
1. Mobile searchlights, Palestine 1936. I identify this truck as a Crossley IGL8.
2. Crossley IGL8, British Military Transport 1939 -1945, Part 13. This truck is likely from the same unit. What is the purpose of the "mailbox" mounted on the cab?
3. Crossley IGL2 or its civilian version, the 30/70 HP?
4.5. Crossley IGL2 in both civilian and military versions http://www.crossley-motors.org.uk/hi...IGL2/IGL2.html