The scenes depicted on the emunctory field, showing our ancient duns and raths and cromlechs and grianauns and seats of learning and maledictive stones, are as wonderfully beautiful and the pigments as delicate as when the Sligo illuminators gave free rein to their artistic fantasy long long ago in the time of the Barmecides.
There are no more uses of "free rein" in the book.
Show samples from other sources
A chill snaked down her spine, but she shook her head, just as a guard entered and told them that Brullo had ordered them to have free rein of the training hall today and to practice what they wanted.
Sarah J. Maas -- Throne of Glass
Didn’t you say that the whole affair had been bungled, and that you should have been given a free rein from the first?
J.K. Rowling -- Harry Potter and the Chamber of Secrets