Sasha had been at Colchester since arriving from Zoo Parc de Beaval in 1998
Staff at Colchester Zoo are mourning the death of its rare Bengal white tiger, Sasha, who has died aged 15.
The exact cause of death has yet to be determined, although he had been unwell for the past few weeks.
Zoological director Anthony Tropeano told BBC Essex he had become one of the most popular animals at the visitor attraction since he arrived in 1998.
"He's going to be very, very sorely missed not just by his keepers but by many hundreds of people," he said.
"He's been one of the most iconic animals here for the last 10 or 12 years and people would often make a bee-line for him."
Mr Tropeano explained Sasha had shown "concerning symptoms" for the past couple of weeks and the zoo's vet Dr John Lewis had ran a series of tests on him.
However the cat passed away in his sleep on Wednesday, 15 December.
"Although nothing particularly remarkable came out of those he was suffering from spinal arthritis, but that's not going to have caused him to have died," he said.
"So we're suspicious there were other things going on, but at the moment we're not quite clear what that is.
"One of the X-rays did seem to show a mass which could be a tumour, but until we have a post-mortem then it's really speculation."
Sasha had a colourful history at the zoo, having achieved notoriety in 1999 when he mauled to death his mate Anna.
"Perhaps in a perverse sort of way why he became as iconic as he did because he was known as the tiger that killed his mate," said Mr Tropeano.
Sasha was one the attractions most popular animals
"The two of them had arrived together and had live together perfectly well for three or four years before being here at Colchester.
"After that we never did put another female in with him and he seemed happy to live a sole existence."
Despite that episode he added Sasha was a "reasonably good humoured" animal.
"I can't say he was ever a cat who you'd think about going in with or sticking your hand through the bars to stroke him, because he was always a typical male tiger and a proud animal," he said.
"But nevertheless for those who looked after him and knew him, he was certainly responsive towards them."