It is the retail prices index thatexcludes the volatile energy cost and food items.
The Central Bank often uses exactly this index on a mid-term horizon (3-6 months) as inflationary target level inflation in the country.
The index calculation unadjusted for the highly volatile components allows for the correct estimation of inflation rate changes for an accounting period.
Effect of market
The index growth or the actual value rise exceeding the forecast is a positive sign for the British Pound.
The significant forecast deviation may have a strong influence on the British Pound dynamics.