London City airport Low flying aircraft Saturday 20th

anyone any idea what this aircraft might have been up to for a couple of hours yesterday, on the most erratic flight path I have ever seen (in green on map below)? Spent a long time circling over SE23 and other areas.

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Or VOR01? No idea but I noticed that one too (it has noisy propellers and was quite low):

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I noticed it as well yesterday whilst with my kid at football practice and again today (in fact in the last 10 minutes, which prompted me to check here). I did wonder whether it was doing imaging sweeps (i.e. for google maps type stuff)

The aircraft - a twin-engine Piper Navajo Chieftain, registration G-FCSL - is owned by Flight Calibration Services. They would probably have been using on-board equipment to test the instrument landing systems (ILS) at LCY (London City).

Cool - I’ve been seeing it all weekend wondering what it was