Not sure what they're using as a source (paywall for that info) but
the ONS seems to disagree. Although i could be reading statista wrong as they're measuring the totally amount of knife crime whereas the ONS measure it per 1k of population, either way while knife crime in London is the highest it's not seen as big an increase from last year when compared to other regions, London +7%, but Gwent is +56%, and Essex is +51%. Even what i think most people would consider the rural idyll of Devon and Somerset saw a rise of 15%.