Coronation grapes are excellent for pie!
Add sugar to the washed grapes and allow them to sit while the pastry is chilling.
After the sugar has soaked in, put the grapes into the bottom pie shell.
Put the top layer of pastry over the grapes and pierce the crust, making sure not to pierce through the bottom layer.
The juice does have a tendency to overflow. Make sure there is a tray on the next rack down to catch the juices while the pie is baking. (It's much easier to clean a tray than to clean the oven.)
It looks a little like cherry pie but the flavour is reminiscent of blueberry. We LOVE this pie!