Trying to remember the title of a children’s book set in Scottish Highlands (west coast). Time shift from C20th to an early time, probably post-Pictish – I think there was a reference to Pictish law as being from the old times; that law (mentioned early in the book) related to the right of anyone to fish & hunt for food they needed. Brochs featured as dwelling places. The time shifting started intermittently, and then the protagonists were permanently in the past. I’m fairly sure that after the resolution there was a return to their original C20th setting. 2 protagonists, 1 boy, 1 girl. Target readership probably pre or early teen. I’d have read it in the mid-late 1960s. My copy was hardback, I’m sure. The author… can’t recall; likely female. My memory suggested a surname like Reece or Treece/Trease but I’ve searched synopses of their books & not recognised it.
Lost Classics of Teen Lit: Name That Book! 