Drop and widen the armhole and extend the shoulder.

Draw the button stand.

On front, redraw the waist dart and manipulate it to open the volume at the shoulder.

Then draw the underbust line towards the side seam…

…and draw some slash lines straight from the waist to the underbust, then from these points to bust point.

Cut through the lines, close the shoulder dart and open the volume in the new cuts.

On the back, erase the dart and mark 3 pleats to take the same volume.

Get the sleeve, widen and flatten the cap to match the armhole measurement and draw the pleat and placket position.

Add a classic collar and a cuff and your pattern is ready!