Greek yogurt dessert in a hurry

I have just returned from a week of family visits in Bristol, Oxford and Lancashire. Looking forward to a leisurely weekend of catching up on sleep and reading, I was horrified to learn that the MM had committed us to a Sunday lunch party and committed me to taking a dessert for 10 people. With no time to go further than the corner shop, what could I do but ring my brother for the recipe for the delicious dessert he had served just a few days ago. He had said that it was quick and easy and so it is:

Ingredients
1 packet digestive biscuits (I used about three quarters of the pack)
500g tub Greek yogurt (0% fat is fine but my shop only had the full fat variety)
1 small can condensed milk (this is the light version, making up for some of the butter to follow!)
Butter
1 large lemon

Method
Put required amount of biscuits in a plastic food bag and crush with a rolling pin. Place in base of serving dish. Pour on melted butter and press mixture down to form base of dessert.

Zest the lemon and reserve for decoration.
Pour yogurt, condensed milk and the juice of the lemon into a bowl and stir until smooth. The mixture will be quite runny but have faith, it will set to a cheesecake consistency.  Pour it on top of the biscuit base, sprinkle the lemon zest on top and put in the fridge.  It will be ready to serve in about an hour but mine will stay in the fridge until tomorrow.

Voila! One delicious dessert to serve at least 10 people, made in less than 10 minutes. Thank you, brother.