All of Heathrow's six runways (not including the original 16R/34L that was relocated to build the CTA) were redesignated at some stage during their lifetime.
While many people will remember when the current 09/27s were 10/28s (the most recent change), prior to that the 06/24s became 05/23s and the 16/34s became 15/33s (all subsequently closed). I don't have those dates to hand, but I probably have them kicking around somewhere.
Don't hold your breath for any more changes in the foreseeable future - the 09s are aligned at approximately 89.7° (true) and of course the 27s are on the reciprocal. But with magnetic variation currently about 0.4° E and an annual change of a measly 0.2° E per year, I don't expect I will ever see them becoming 08/26s (nor reverting to 10/28s) in my lifetime.