A male tiger mauled his intended mate to death after they were put in the same enclosure.
Asim, a seven-year-old male Sumatran tiger, killed 10-year-old tigress Melati after being moved to London Zoo as part of a European-wide conservation breeding programme.
It was hoped that Asim, who came from a safari park in Denmark, would mate with Melati and the pair had been in adjoining pens for more than a week so they could slowly become acquainted with each other.
But he attacked her after they were put in the same 2,500sq metre enclosure.
Zoo staff desperately tried to distract Asim with loud noises, flares and alarms but he overpowered Melati and killed her.
A spokesman for London Zoo said staff were “devastated” and “heartbroken”.