At about 8pm on Saturday, December 1, 2018, emergency services were called to a rural property in Denman, following reports of a concern for welfare.

On arrival, Hunter Valley Police District officers found a 71-year-old man had died.

He was later formally identified as Douglas Thrift.

A post-mortem examination revealed Mr Thrift had a fatal concentration of the highly-toxic strychnine in his system. Strychnine is a restricted substance.

Detectives from Hunter Valley Police District established Strike Force Farview to investigate the circumstances surrounding his death.

Hunter Valley Police District crime manager Detective Inspector Matthew Zimmer said detectives would leave no stone unturned in this investigation.

"From all accounts, Douglas Thrift was a loving father, grandfather and husband, who really enjoyed playing sports - especially rugby union, cricket and golf - and was happiest working on his farm," he said.

"Strike Force Farview investigators are trying to piece together how a fatal amount of this substance came to be in his system.

"Our detectives are keen to speak with those who saw or spoke with Mr Thrift in the days leading up to his death in early December 2018.

"We're also interested in speaking to any farmers, or other members of the public, who have found strychnine missing from their properties."

Anyone with information that may assist Strike Force Fardiew investigators is urged to contact Crime Stoppers: 1800 333 000 or online