Re: It's all in the 'title'
Farmer is not on the list of example recognised professions*, however a signatory can also be a "person of good standing in the community". Being, or being retired from being, a chairman or director of a limited company is on the list, as are many other "professions".
Personally I qualify more than once, as a "manager or personnel officer of a limited company", "director, manager or personnel officer of a VAT-registered company", "member, associate or fellow of a professional body**", "local government officer" and "civil servant (permanent)" (although the last two were a long time ago).
*All this applies to UK passport countersignatories.
**Institute of Mathematics and it's Applications for the record and I do have Chartered status.