I recently came across information about a rather peculiar building that was on the airfield at RAF Grimsby. Known as the AML Bombing Teacher (AML from Air Ministry Laboratory) it was based on an earlier version called a Vickers-Bygrave Bombing Teacher. This ingenious device provided training for air bombardiers.
Developed from the mid-1920s (the National Archives at Kew have films for the device) the 'teacher' projected a scrolling image of an aircraft's flight and target onto the floor. Various heights could be also be selected. The bomb aimer peered down a bomb sight from an elevated platform at the image and similar to a real bomb run he could communicate with the 'skipper' to make course changes which adjusted the image accordingly.
The bomb aimer would then 'release' his bombs. His results would then be compared to the correct bomb release point.
A two-story building was built at RAF Grimsby to accommodate this apparatus, It appears that many of these buildings were constructed at Operational Training Units (OTUs) but main stations also acquired them like Waltham.
Control Towers website has images of the building at Waltham in question.
As and when information is found I'll post to this blog.