Gran used to make these (back in the 40's) - just saw the recipe on a Facebook post.

RECIPE

1. Preheat the oven to 180°C. Grease and line a baking sheet.
2. Break McVities Digestives on the perforated lines into smaller 1-by-3-inch rectangles, and lay them out on the prepared baking sheet as close together as possible, covering the entire sheet.
3. Mix 2 sticks of butter and 1 cup of brown sugar in a saucepan over medium heat. Once the butter and sugar mixture comes to a bubble, add 1 cup of chopped pecans and stir together.
4. Pour the mixture evenly over all of the crackers. Bake for 10 minutes and then cool, about 30 minutes. Break or cut into pieces to serve.