Sir

What Walker somehow fails to mention in his dismissive review1 is that Rose's book includes a devastating critique of Walker's own work on the subject. Re-examining the technical records on which Walker based the central thesis of his 1989 book4, Rose shows that Walker misrepresented crucial documents and suppressed essential evidence.

Ten years ago, Walker claimed to have uncovered archival documents proving that German physicists had “performed the same sort of experiments, had made the same type of calculations, and had come to similar conclusions as the Allies — for example the estimate of explosive critical mass”. As Rose demonstrates, this interpretation can be made to seem plausible only by the most convoluted and selective reading of the evidence.

A key 1942 German progress report, for example, cited by Walker to demonstrate that Heisenberg knew the critical mass of a uranium-235 bomb to be small, does contain a parenthetical speculation that with plutonium (then a hypothetical element) a small critical mass might obtain. What is described in the main text of the report, however, is the unworkable multi-ton reactor-bomb first intimated by Heisenberg in 1939. By citing only the parenthetical remark while suppressing the report's substance, Walker transforms contrary evidence into support for his thesis. Inconvenient technical reports by Heisenberg's research assistant Paul Müller elaborating the misguided reactor-bomb concept go unmentioned in Walker's account. An oral history interview with wartime scientific intelligence officer Sir Charles Frank forcefully describing Heisenberg's mistaken estimate of the critical mass is likewise suppressed — Walker cannot have been unaware of it since it was he who conducted the interview. Thus did Walker succeed in “misrepresenting not only the content of the document[s] but also the whole history of the German atomic project”.

Reading Walker's review, one would never know any of this, or that such objections had ever been raised before3,5,6. “Rose's book does not really have a conclusion,” writes Walker, while suggesting that there is little in it that could possibly interest the readers of Nature. Having made the unfortunate decision to review a book that contains discrediting revelations about his own scholarship, Walker might have taken the opportunity to address the disturbing issues it raised. At the least, readers are entitled to a disclosure of self-interest. Instead, Walker chose the dismal principle he has followed before, si incommoditas est, non est. Whether a discordant fact, an inconvenient document, or a detailed study putting his claims to the test: if it doesn't fit, it just didn't happen.