Since November, in a clinical, modern conference center in central London, the public hearing of an inquiry into Britain's role in the Iraq war has been taking evidence. It has been a very British affair. Chaired by a former public servant, Sir John Chilcot, the inquiry has been marked by polite probing rather than electrifying cut and thrust. Yet for all the lack of drama to date, seats for the appearance of former Prime Minister Tony Blair, expected to take place Jan. 29, are in such demand that a ballot for them has had to be organized.

The reason is not — or not just — that Blair still retains an element of star quality, although he clearly does. There is also a sense that part of his personal Iraq story remains untold. That, despite his evidence to previous...