Which British author wrote the adventure novel "The Vivero Letter"?

Desmond Bagley (29th October 1923 - 12th April 1983), was a British author with 16 novels published. Several of these were made into films, including "Landslide", "The Freedom Trap", "The Enemy" and "The Vivero Letter". During WWII, Bagley worked in the aeronautics industry, a speech impediment (stutter) exempting him from military conscription.

"The Vivero Letter" starts with the main protaganist's brother being murdered, seemingly for an old fruit bowl. However, an American millionaire, two archaeologists, and a gangster are all trying to solve the mystery of the Vivero letter, which turns out to be the location of a hitherto unknown Mayan city. The "fruit bowl" turns out to be one of two, which together show maps which give the location of the city described in the letter. An expedition is set up, and after some twists and turns the true "Treasure" is revealed.