Veronica Packman disappeared from her family home in Bournemouth in 1985.
Her daughter Sam Gillingham, then 16, came home from school to find a note, supposedly from her mother, along with her wedding ring.
The letter said that she was leaving their family.
The year before, Causley moved his lover Patricia Causley into the house and later changed his surname to hers.
It wasn't until 10 years later, when Causley was jailed for two years for trying to fake his death in a boating accident that he was found guilty of her murder.