An interesting and fascinating subject, to those have inquiring minds: Historical context in terms of Radio Direction Finding or RDF, which originally was called Huff Duff during World War I and II, but still actively being used on the Higher Frequency bands. With the ability to now programme in noise and search capabilities we now have the capability to use Time Distance of Arrival (TDOA) with three or more passive receivers with GPS built in. KiwiSDR is a good example and you can try it yourselves at www.sdr.hu
If anyone is bored over the festive season, I would recommend experimenting and trying it out.
Gatwick Airport could have used the same techniques to find the source of the Drone controller too, had they applied the appropriate techniques.
This is not a subject for answering, it is merely an interesting aspect of radio communications, with fascinating historical aspects, which only now have recently made it possible to carry out Time Distance of Arrival calculations accurately to ensure that reports can be passed on to authorities under the International Telecommunications Union, who globally support the frequency allocations for all nations around the world and as part of this - there is an international Intruder Monitoring group, who have had major difficulties from the past 90-100 years providing radio direction finding to a reasonable accuracy over long distances.
Although the next subject will how to detect rogue Internet of Things (IoT) and IIoT) devices, accurately enough, so that adequate screening can be put in place or security controls to minimise the impact of such devices on organisations. But not a lot of organisations, have even considered - perhaps they are still caught in monitoring drones around airports and how to detect the source i.e. the operator?
At the Security Congress, one of the principals of Secure802 gave a session on IoT devices, and some background/stories on radio as well. If anyone is in the hunt for RF engineers to augment security staffs for this kind of work in the US, Verizon Wireless just let a lot of folks go, and I'm sure there is some top talent on the street right now. (I used to work there as well) Interference source hunting has been part of their bread and butter for years in the Performance space, especially clearing spectrum for the LTE launch several years ago. These skills would easily transfer to rogue device, remote controller, etc. detection and locating.