Ms Britton, 52, was shot in the head at her Airlie Beach home 22 years ago and police had believed she knew her killer.

"It was a tragic, violent end to her life, of a lady that is in her own house minding her own business," Detective Senior Sergeant Chris Knight said.

Brisbane homicide detectives on Thursday afternoon arrested a 51-year-old man, a Port Neill resident who previously resided in Airlie Beach.

"The individual that was arrested today has been spoken to before in fairly recent times by us," Det Sen Sgt Knight.

He said investigators think there are more revelations to come.

"There are still people out there who hold information in relation to this," he said.

Cold case detectives had recently followed up leads in South Australia and north Queensland, and this month said the murderer was a "close associate of hers".

Det Sen Sgt Knight also said the killer had confessed to others and called for them to come forward.

Ms Britton's son Adrian Britton last month said suspicion had torn his family apart, and he only trusted his younger brother with "every other person on the planet" considered a suspect.

The attacker would have had to get past a Rottweiler who was fiercely loyal and protective of her and her rural home.

Ms Britton's body was found after relatives could not reach her and went to check on her.

When they arrived, the front door was open and the dog was standing on the verandah.

There were no signs of a struggle and Ms Britton's handbag, containing cash, was not touched.

A shotgun missing from the property has never been found.

The man expected to be charged over her murder will front court in Brisbane on Friday, Det Sen Sgt Knight said.

Australian Associated Press