Tea with the Queen

Normal sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9. Sandwich sums: numbers outside the grid indicate the sum of all cells between 1 and 9 in that row or column, excluding 1 and 9 from the sum. Fortress cells: Shaded cells are fortress cells and must be larger than all orthogonally adjacent cells. All possible fortress cells are shown. That is, there is a negative constraint on fortresses and any unshaded cell must be orthogonally adjacent to at least one larger digit.