According to a press release dated 15 February 2017, the Bank of England acknowledged the concerns of some regarding trace amounts of animal-derived tallow in the production of the polymer substrate used in the 5-pound note introduced on 13 September 2016, as well as the 10-pound note scheduled for September 2017 introduction. However, the bank has decided not to withdraw the notes nor stop their introduction because to do so would incur substantial costs, but changes may be made for the new 20-pound note due for introduction in 2020.
Courtesy of Mark Irwin.