Video report by ITV News Correspondent Geraint Vincent
Wayne Lotter was co-founder and president of PAMS Foundation, which was credited with helping to arrest thousands of poachers and traffickers over the years.
The 51-year-old, from South Africa, was killed last week while travelling through the city of Dar es Salaam. He had received many death threats in the past.
Speaking at his memorial service, Iain Douglas-Hamilton, founder of Save the Elephants, said Mr Lotter had done an “enormous amount” for the cause.
Mr Douglas-Hamilton said: “He was incredibly determined. Once he latched on to what should be done, he was going to do it.
“He always took the back seat, he never went for the limelight. On the contrary he would advance those people at the sharp edge who were taking the risks."
Krissie Clarke, a fellow co-Founder of PAMS and one of Mr Lotter’s closest friends, said the team was ready to continue his legacy.
She said: “I was fortunate to be able to work with him, have him as a mentor and have him as my closest and best friend.
“Our war here is not over and there’s still a lot to do. The PAMS team, I think we’re all ready to go for it and continue the legacy that he started.”
Among his many achievements, Mr Lotter will be remembered for supporting and funding Tanzania’s top anti-poaching task force, the National and Transnational Serious Crimes Investigation Unit (NTSCIU), which has made some of the biggest arrests in the country.
The NTSCIU has detained thousands of poachers and ivory traffickers since it was set up, including the so-called 'Ivory Queen' - aka Yang Feng Glan - a Chinese woman who is accused of running a $2.6 million ivory trafficking ring in a case that is ongoing.
Tom Milliken, the elephant project leader at wildlife trade monitoring network Traffic, said: “Wayne was able to build bridges and work with people that people in the limelight will never even know about, and I don’t know how we replace him.”