We need to hire a British to American translator!
Two references to crown of chicken that I could find make it seem like it is more than just the breast.
The Good Food Channel
website doesn't give a great definition, under ingredients it just simply says: chicken crowns (legs and wings removed)
And a recipe for roast chicken crown on Cooking It - Channel 4
includes the instructions: Spread the breast with half the butter and place a few thyme sprigs in the body cavity
... and under Recipe Tips the #1 tip says: Ask your butcher to make the chicken crown if you like. Alternatively, remove the legs, wings and breast bone from a whole chicken yourself.
that by breast bone they mean the keel bone, not the ribs under the breast since later in the recipe, after the chicken is first roasted, it says: Remove the chicken from the oven and place on a board. Using a sharp knife, carefully take the breasts off the bone
Now, considering that a large roasting
hen can run 6-8+ lbs, an 8-lb chicken minus wings and legs (I assume
the leg includes the thigh) is a little more imaginable.
At 325°F (170°C - Gas Mark 3) I'm guessing 2 1/2 - 3 hours since we don't have to worry about the dark meat?