... or just a radar processing glitch ?
This, from Heathrow's own WebTrak system, appears to show an extremely close encounter between an Air Canada 737 MAX and a Swiss CSeries on converging tracks inbound to LHR:
Heathrow WebTrak
Given that it's from last weekend, it would no doubt have been all over the media by now had it actually occurred, so presumably it's an artifact from NATS' radars.
Cany anyone account for what might have caused it ?