Thank you MathsRC for the interesting analysis. There has definitely been an increase in the marks needed to achieve a pass at GCSE since the introduction of the Gove" reforms ". However, according to Ofqual the grade boundary for a particular exam is determined by the level of achievement predicted from a cohorts Yr6 Sats. If everyone falls short of the expected level of achievement, the grade boundaries will be lower in the belief the paper was difficult, and vice versa.
By this logical it is students improving at Yr 2 which has resulted in the higher pass mark year on year. I have it on good authority from the Tooth Fairy there was no political interference at all.