He had just given information about a two jewellery store break and enters in southern Queensland that resulted in the arrest of two people.

Mr Allen, a 22-year-old labourer, was last seen in a car at Warwick with someone he knew about 5pm on April 18, 1964.

His disappearance resulted in the burglary charges being withdrawn.

What followed in the next half-a-century was a police investigation and an inquest which found that he was likely murdered in Queensland's southern downs region.

Now 80-year-old Vincent O'Dempsey has been charged with murder in what police believe is the oldest cold case resolution in Australia.

The elderly man appeared in Brisbane Magistrates Court on Tuesday afternoon. He was remanded in custody to reappear in the same court on September 16.

O'Dempsey, who knew Mr Allen, was interviewed by police in 1975 and 1979 over the suspected murder.

His arrest comes after the state government last month announced a $250,000 reward for information leading to the conviction of the person responsible of the murder.

In addition to the reward money, indemnity from prosecution was to be recommended for any accomplice who was the first to hand over information leading to a conviction.

Detective Senior Sergeant Tara Kentwell on Tuesday asked for people with any information about the case to come forward.

Australian Associated Press