Heat the oil in a large pan until very hot, but not smoking.
Tip in the popping corn, reduce the heat to low and quickly cover with a tight fitting lid and wait for the corn to start popping.
When the popping has ceased, remove from the heat
Line a baking tray with non-stick baking paper.
Put the sugar, syrup, butter, salt and vanilla into a large heavy based pan and heat gently heat until sugar has dissolved.
Increase the heat slightly and cook without stirring for 5-7 minutes. Stir in the bicarbonate of soda, then add the nuts and popped corn and stir to coat the kernels.
Quickly spread onto the baking tray and leave to set. Break into chunks when cold.