Ange Postecoglou’s first foray into the tournament could scarcely have been worse already, but his men hit a new low after less than six minutes at the Santiago Bernabéu.
Moritz Jenz was the culprit, handling Fede Valverde’s shot inside the area and giving referee Stéphanie Frappart no choice but to award a penalty, which Luka Modrić dispatched with ease.
Los Blancos were two up before the midway point of the half, again netting from the spot following a VAR intervention, with Vinícius Júnior’s shot striking Matt O’Riley’s arm from close range.
The 2-0 HT scoreline only told half the story though, and Thibaut Courtois needed to be alert to save efforts from Kyogo Furuhashi and Reo Hatate, while the visitors even had a penalty of their own when Ferland Mendy hauled down Liel Abada in the area.
On this occasion, there was no need for a Frappart intervention, as Marco Asensio fired beyond Joe Hart from just inside the area.
Shortly after the hour mark, the hosts extended their lead even further, Vinícius tapping Valverde’s cross into the corner.
Celtic, meanwhile, are now winless in ten trips to Spanish clubs, and will need to wait until 2023/24 for their next European encounter.