Did a west highland terrier ever won best in breed?

Yes, West Highland White Terriers have won Best in Breed at the Westminster Kennel Club Dog Show multiple times.

Here are a few examples:

* 2017: "Dundee" (Ch. Windborne's Dundee, owned by Anne Fowler, breeder: Wendy B. Russell) won Best in Breed.

* 2012: "Dakota" (Ch. Willow Creek's Dakota, owned by Karen and Michael Gelfand, breeder: Brenda and Richard Smith) won Best in Breed.

* 2005: "Ch. Glencoe's Show Stopper" (owned by Bill and Karen Smith, breeder: Bill and Karen Smith) won Best in Breed.

These are just a few examples, and there have been many other West Highland White Terriers that have achieved this prestigious title throughout the history of Westminster.