Why the beep? Hesitant driver, punishment pass

VW Combi driver for some reason decides change lane to follow me (rather than stay in existing lane and overtake) then follows very closely behind, then honks horn and close-passes me. In rush hour traffic. Only to be caught at the next set of traffic lights. Totally unnecessary - I guess these drivers have main character syndrome.

Won't bother to report as Swiss authorities don't accept cycle camera footage. Or dashcam.