If you have shares that have vested from an employee share plan and you hold a share certificate, you need to sell your shares through a stockbroker. You can also sell your shares through Diageo Registrars (Link Asset Services) and their share dealing service.
Phone: 0044 371 277 1010
Mail: Diageo Registrar
PO Box 521
If you hold shares that are still part Profitshare or Salary Foregone and they're between 2 and 3 years old, you should contact the Diageo Shares Office (firstname.lastname@example.org) for further information. If you have an Executive award that's available to exercise, then you can transact online through the MyDiageoShares portal. Information on exercising an executive award can be found here;