Nigel Pascoe QC, for the prosecution, told Bristol Crown Court that Joan Main, a mother of three, disappeared in January 1973, two days after moving into a house at Blunsdon Road, Swindon, which her former husband David Main had been renovating.
A short time later, it is alleged, Mr Main buried her body in the garden of a house at Goddard Avenue, Swindon, which was owned by his business partner, Madeleine Cavey, with whom he had been having a relationsip.
Mr Main, 60, of Broadwell, near Lechlade, Gloucestershire, pleads not guilty to murdering his former wife, who was then 35, between 21 and 31 January 1973. When he was arrested in March last year, excavations began at the Goddard Avenue house.
Mr Pascoe told jury members that they were concerned with 'a dreadful burial', and a prolonged, callous and cunning deception to cover up the murder. It meant Mr Main living a lie for 20 years, hiding the truth from his children and former in-laws.
Mr Main had claimed that his former wife had left to start a new life with another man, and he forged a letter and a birthday card to her mother to back up his story, Mr Pascoe said.
By 1973, Mrs Main had overcome a divorce and was rebuilding her life in a home restored by her former husband, he said. 'She had everything to live for. Yet on 20 January, on the 13th birthday of her eldest child Lyn, she disappeared without trace.'
The prosecution contends that, 20 years later, her body was found in the oildrum in the rear garden of 128 Goddard Avenue.
'In all probability Joan Main had been strangled, and the Crown say that David Main killed her. That is the chilling and tragic conclusion we shall ask you to draw,' Mr Pascoe told the jury.
After his divorce from Joan Main, the defendant married Madeleine Cavey, and moved to her flat at 27 Goddard Avenue, opposite No 128, the house that Ms Cavey later bought.
They were divorced in 1984, and Ms Cavey committed suicide five years later.
The trial continues today.