Adair Turner is about to present Gordon Brown with one of the biggest political challenges the chancellor has faced since Labour came to power in 1997. When the 50-year-old business consultant-cum-policy wonk delivers his landmark report into the looming pensions crisis next week, the details will probably go over most people’s heads.

But, even before he has published a single word of his report, Lord Turner has achieved something few people have ever pulled off before. He has forced this most formidable and powerful of chancellors to start fighting to maintain his grip over one of the central domains of Treasury policy. The Treasury has let it be known that it regards the independent Pensions Commission’s central proposal for a bigger basic state pension, rising in line with earnings, as unaffordable.