Preheat you oven to 170C/325F/Gas mark 3 and lower one of the racks to the lower third of the oven. Line a 2 pound loaf tin with baking parchment, make sure to leave a little overhang for easy removal.
Pulse, using a food processor or bash the digestives/graham crackers and until they are a fine crumb.
Then pulse or bash the pistachio's until they are in a coarse crumb.
Mix the cookie crumbs, pistachio's and melted butter together. Then press the mix into the bottom of the loaf pan, pressing down to make sure everything fully sticks together.
Pop the base into the oven and bake for 20 minutes.
Meanwhile, mix the cream cheese, sugar, sour cream, the egg, vanilla extract and the lemon juice and zest until you have a smooth batter.
Take the base out of the oven and reduce the heat down to 150F/300F/Gas mark 2 then pour the batter over the base. Don't worry if the base is warm.
Place your loaf pan into a roasting dish and add a couple of cups of boiling water to the roasting pan and place the whole thing into your oven.
Bake for 40-45 minutes, you are looking for your cheesecake to be starting to pull away from the edges and still have a slight wobble in the middle. Once baked allow your cheesecake to cool down to room temperature in its tin before placing it into the fridge for at least 6 hours.
This cheesecake is perfect plain or you can sprinkle a few crushed pistachio's, rose petals and extra lemon zest on the top.