Heat the oil in a large, heavy-based pan over a medium heat

Add the butter and melt, swirling it into the oil with a wooden spoon

Pour in the corn and add a pinch of salt. Put the lid on the pan. The corn will start popping after about 1 minute and carry on for another 2-3 minutes

When the popping sounds slow down to more than 4 or 5 seconds between pops, remove from the heat and leave to cool slightly in the pan

In the meantime, add the butter, syrup, sugar and water to a saucepan over a medium-high heat. Stir constantly with a wooden spoon until the butter has melted and sugar dissolved

Bring to the boil and let it bubble rapidly for 4-5 minutes, stirring throughout, until the mixture is a dark, toffee colour

Pour the toffee sauce over the popcorn, and stir to coat all the kernels

Leave to cool slightly and let the toffee sauce harden for around 5 minutes before serving