There used to be a small unit near Glasgow called 'Glasgow Bombplot'. This was basically a radar unit that could very accurately track an aircraft, and had the equipment to mechanically draw a trace of the ac track over the ground on a large strip of paper.
The bomber crew would call the bombplot and declare lots of info, such as bomb type [different bombs had different freefall characteristics] and a host of other info. The nav radar, using the radar screen and bombing computer, would then carry out the bombing run [the bombing kit was linked to the autopilot] - effectively he 'flew' the whole run. A tone was set off on the r/t and stopped at bomb release.
The bombplot crew then took the trace, applied all sorts of factors, and measured where the bomb would have impacted relative to the target. This was then passed to the crew on the radio by code. To see a stream of aircraft at regular intervals on the same track would suggest either an exercise or a competition, where all crews fly the same route and drop bombs on the same target.
These bombplots were dotted round the country - Lindholme, Devon, London, springs to mind [there were others]...