There is no UK air defence radar coverage of the Channel Islands area at relevant altitude. MoD say they have no information on any possible radar contacts. The Channel Islands Air Traffic Control Zone lies within the French air defence zone. A French long-range Centaure air defence radar with coverage of the area is located close by at Maupertus near La Hague on the Cotentin peninsula.
An early inquiry to the French authorities eventually produced a negative response. CCOA (Centre de Conduite des
Opérations Aériennes) informed us n1Email to Jean-Francois Baure, 07.06.07: Suite à votre demande j'ai fait faire les restitutions radar de tous les
mouvements aériens détectés dans la région que vous m'aviez décrite et pendant le créneau horaire suivant:
23/04/2007 entre 14h09 loc et 14h 18 loc.heure anglaise. Aucun phénomène (hormi les aéronefs sous contrôle civil
ou militaire) n'a été detecté par notre réseau de radars.
that a reconstruction of all aerial movements in
the region from the radar network log revealed no unidentified phenomenon or aircraft in the time frame of interest
(1409-1418Z). However they also informed us that the radar data would be routinely dumped after only a few hundred
hours. At this time CCOA stated that they had not yet been in receipt of an official request for radar data by GEIPAN n2GEIPAN (groupe d'études et d'informations sur les phénomènes aérospatiaux non identifiés) is the official UAP
investigation group of CNES (France's National Centre for Space Studies). https://www.cnes.fr/web/5038-geipan.php).
We pursued inquiries through GEIPAN but they were unresponsive. We then approached a French researcher associated with NARCAP n3National Aviation Reporting Centre on Unidentified Aerial Phenomena, a US air-safety oriented organisation. Coauthor Martin Shough is a Research Associate for NARCAP. https://www.narcap.org who was also connected with individuals working for GEIPAN's "college of experts". We learned informally via this route that GEIPAN had been independently advised by French air defence sources that no radar data were extant, having been destroyed after eight weeks.