Campaigner has used the idea drawn from Discworld novels to register the disproportionate effect price rises have on the lower paid

Terry Pratchett’s estate has authorised Jack Monroe to use the “Vimes Boots Index” as the name of her new price index, which is intended to document the “insidiously creeping prices” of basic food products.

The author’s daughter, writer Rhianna Pratchett, said her father would have been proud to see his work used in this way by the anti-poverty campaigner. Monroe was prompted to create her index after inflation jumped to 5.4% last week, and she found herself “infuriate[d]” that the index (the consumer price index or CPI) used for this calculation “grossly underestimates the real cost of inflation as it happens to people with the least”. She laid out how the prices of “value” product ranges in supermarkets had soared over the last decade – rice in her local supermarket had increased in price from 45p for a kilogram bag last year, to £1 for 500g, a 344% increase – and how the number of value products has shrunk. She was soon working with economists, charities and analysts to compile her own index.