There are different ways of measuring inflation.
The Consumer Price Index (which is the government's preferred measure) for annual inflation was running at 2.4% at the end of October. A year before, it was 2.3%. Compounding these figures, over a two year period, gives an aggregate rise of 4.8%
However, the Retail Price Index for annual inflation was running at 3.7% at the end of October. A year before, it was at 2.5%. Compounding these two figures, over the two year period, gives an aggregate rise of 6.3%.
http://www.statistics.gov.uk/CCI/nugget.asp?ID =19
Chris