If there was no chase it could probably be proven with video evidence from all sorts of cameras, plus the GPS trackers fitted to many police cars, and the GPS in all the officers' phones. (There'd probably be 9 officers, because armed reponse vehicles usually work in threes. )
Edit: and the police control room cooperates with chases. Senior officers have to be notified of some chases. I would think that three armed reponse vehicles chasing a vehicle with a firearms APR tag is something that the senior officer in the control room would be informed of immediately. Plus the senior officer is supposed to give permission for ramming, if circumstances permit.
So you'd have to get a very large number of officers, including at least one inspector, to tell the same lie, if you want to concoct a chase.
Another edit: the police cars have dashcams! Of course they do. The IOPC is "reviewing a large amount of footage including from body worn video, police car dashcams, police helicopter and CCTV"
Safe to say that this notion of a faked chase is yet more epic bullshit.
Statement from IOPC Director General Michael Lockwood regarding fatal police shooting in Lambeth | Independent Office for Police Conduct