Melati. Credit: ZSL London
The 10-year-old female was introduced to seven-year-old Asim on Friday 8 February, ten days after he arrived at the zoo.
A statement from the zoo said their meeting was 'carefully planned' and admitted it was 'high risk', but added it was the next step to take after the pair showed 'obvious positive signs'.
The ZSL statement said: "This morning, new male Sumatran tiger Asim was introduced to Melati for the first time. Since Asim's arrival ten days ago, the two tigers were in adjoining enclosures, where they could see, smell and react to each other before being brought together.
"Following careful monitoring of the tigers' reactions to each other, zoo experts observed obvious positive signs, and felt it was the right time to introduce seven-year-old Asim, and ten-year-old Melati.
Melati in Tiger Territory. Credit: ZSL London
"As with all big cats, introductions, however carefully planned, are always considered to be high risk."
It goes on to explain how the beginning of the two tigers' introduction went as 'predicted' but things went south soon after.
"This morning, the two tigers were in separate paddocks and the adjoining door was opened to allow them to meet. Asim approached Melati and, as expected by keepers, the two tigers were initially cautious," the statement said.
"Their introduction began as predicted, but quickly escalated into a more aggressive interaction. Zoo staff immediately implemented their prepared response, using loud noises, flares and alarms to try and distract the pair, but Asim had already overpowered Melati."
Zookeepers who acted quickly were able to safely get Asim back in a separate area, but it was too late.
The statement continued: "Zookeepers were eventually able to secure Asim in a separate paddock so that they could safely get to Melati where our vets confirmed that she had sadly died.
"Everyone at ZSL London Zoo is devastated by the loss of Melati, and we are heartbroken by this turn of events.
"Asim was moved to ZSL London Zoo as part of the European-wide conservation breeding programme, and it was hoped that the two tigers would be able to breed in the future."
The Tiger Territory was closed for the rest of the day while the team tended to Asim.
Featured Image Credit: ZSL London