The changes take place at the tops of the people and supply chain departments.
The two appointments are a result of Gallot's decision to move on after 11 years.
Gregan started his career in New Zealand's wine industry fresh out of university in 1983.
Geary has been interim CEO for the last two months.
Gregor has been a non-executive director at the company for the last year.
Diageo chair Sir John Manzoni said Rishton brings 'a track record of creating sustainable, long-term…
The revised structure of the senior executive team will kick in next month.
Before focussing his attention on the vodka category, McDonnell's speciality was tequila with Patron.
Smith is president of family-owned Connecticut-based wholesaler Eder Bros.
