Anybody about - need help with a mortgage on a field!

Sarah-Lou

Client is a dog agility instructor, runs classes all week from a field and she only uses it for that (I know that because she is a friend). It is mortgage on a repayment/interest mortgage. Does it come under the same ruling as a mortgage on a premises - you can only claim the interest as an expense? I'm googling/searching to the best of my ability but not getting anything