Robert Brown admitted killing his wife in October 2010 but denied that it was murder on the grounds of diminished responsibility, London's Daily Telegraph reported.
In addition to his earlier admission of manslaughter, the jury convicted Brown of preventing a coroner from holding an inquest by disposing of a body.
He told the court he was suffering from extreme stress over their divorce when he attacked his 46-year-old wife with a claw hammer on the doorstep of her sprawling mansion near Ascot.
She received at least 14 blows to the head, testimony at the eight-day trial indicated.
Brown then wrapped the victim in plastic sheeting, covered her head with a plastic bag and put her in the trunk of his car.
He drove to a nearby park where he had previously buried a large plastic box that perfectly fit her body.