Marcin Kasprzak, 25, was found guilty of trying to kill Michelina Lewandowska, 27, who escaped the shallow grave a wooded area near Huddersfield, the BBC said. Kasprzak had used a stun gun to incapacitate her May 28 at their home.
A co-defendant, Patryk Borys, 18, of Huddersfield, was acquitted, the BBC said.
Authorities said Kasprzak had wanted the mother of their 3-year-old son Jakub out of the way because he feared she would take the boy with her back to their native Poland, The Daily Telegraph reported.
It was a symbol of Kasprzak's love for Lewandowska that saved her life -- she used her engagement ring to cut herself out of the box and reach the surface.
The newspaper said the Leeds Crown Court jury reached its verdict after three days of deliberation. Kasprzak, a meat plant employee who contended he only meant to frighten Lewandowska, a clothing factory worker, is to be sentenced Jan. 13.