It's the condiment that divides a nation.

Salt 'n' sauce is part of the chip shop tradition in and around Edinburgh, but salt and vinegar still reigns supreme across the rest of Scotland.

Inspired by a question from reader Iain Simpson, we tried to find out why Scotland is split over what you should put on your chips - and see if it was possible to define the boundaries of chippy sauce country.

Video by Zara Weir

Research by Louise Wilson