Used different ingredients.
I only had self raising flour instead of plain flour, and raw sugar instead of caster sugar. Gamble taken. As I watched the oven in panic as they began to get bigger and bigger, I thought I would disappear into a mountain of biscuit. The only thing I ended up with was biscuits the size of my head that I had to try to chisel off the baking tray. Though they tasted quite good. Thank you.