Why is there animal fat in the new £5 note?

The Bank of England has admitted that the new polymer £5 notes contain animal fat, outraging many vegetarians and vegans.

The new notes have been championed as far longer-lasting than the paper variety: they are harder to tear, waterproof and harder to counterfeit. Following the introduction of the new £5 this summer, a polymer £10 featuring novelist Jane Austen will go into circulation next year, and a polymer £20 will follow by 2020.

However, following questions about the make-up of the notes, the Bank has confirmed in a tweet that "There is a trace of tallow in the polymer pellets used in the base substrate of the polymer £5 notes."

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It points out that tallow is also used in other common household products such as candles and soap.

However, a petition calling for the Bank to stop using the tallow has reached more than 6,000 signatures, with many of the people signing saying that they'll refuse the new notes. Some say they aren't either vegetarian or vegan, but still find the use of animal fats unpleasant and unnecessary.

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"This is unacceptable to millions of vegans & vegetarians in the UK," the petition reads. "We demand that you cease to use animal products in the production of currency that we have to use."

According to the fact-checking site Snopes, the tallow is derived from beef fat - possibly making it problematic for devout Hindus too.

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The suet-like substance is believed to be used as a source of stearic acid, which acts as a lubricant and neutralises trace additives in the notes. There are vegetarian alternatives, although these are likely to be more expensive.

It's notoriously difficult for vegetarians and vegans to avoid animal products, which pop up in the unlikeliest of places. Plastic bags, shampoo, fabric conditioner and toothpaste can all be out of bounds.

However, there are alternatives to all of these, whereas £5 notes are a different matter - unless vegans and vegetarians start insisting on using coins for everything, that is.