Of course it did, because that was 1971 I think. My mistake. Also I overlooked that the pound stayed the same but the definition of a penny changed, another silly error. Whoops.
It would have been 240% rather than 2.4%, though, because the value of a new penny was equivalent to the vale of 2.4 old pence, making for an effective change of (2.4/1)*100% = 240%. Since inflation is measured by the pound it doesn't matter, though.
(I think there's another error, in that inflation is usually measured as (new-old)/old rather than just new/old. But never mind.