By Colin Holmes
Routledge, £14.99

We shall never know just how many Britons, during the Second World War, were actually (never mind actively) sympathetic to the Nazi cause. But we do know that three of them were executed for their treachery.

One was the emotionally disturbed John Amery, who ought to have ended his days in a psychiatric institution but was hanged in Wandsworth prison on December 19 1945; 16 days later, former soldier Theodore Schurch was hanged at Pentonville. The previous day, also at Wandsworth, William Brooke Joyce - known both to his enemies and his friends as "Lord Haw-Haw"on account of his affected broadcasting voice - had also met his end in the hangman's noose.

The controversial circumstances of Joyce's trial have been exploited to help paint him as less evil than he actually was. Born in the USA in 1906, Joyce had used a fraudulently obtained British passport to travel to Germany, where in due course he became the leading English-language broadcaster of the Nazi state. As Professor Holmes tells us - in what must surely rank as the definitive Joyce biography - in today's internet age it is difficult to imagine the unique place and power of the radio in the war years. Joyce was a smooth talker (he had, after all, obtained a first-class honours degree in English from Birkbeck College London in 1927) and there can be no doubt that his broadcasts ("Germany Calling") attracted a following among British audiences.

But was Joyce actually British? At his trial, the prosecution argued that, whether fraudulently obtained or not, his British passport - to say nothing of the fact that he had served briefly in the British army - was proof positive that he had placed himself "under the protection of the British crown." This was a tendentious argument, which the jury nonetheless accepted.

Much less contentious was the fact that the trial judge - Mr Justice Frederick Tucker - had, as early as 1940, publicly denounced Joyce as a traitor. Why, therefore, was Tucker allowed to preside over his trial?

The circumstances of Joyce's trial were indeed perverse but this should not blind us to the fact that Joyce was a totally unrepentant, narcissistic Jew-hater. A member of the BUF, he had actually parted company with Oswald Mosley, whom he did not consider sufficiently antisemitic.

The fundamental strength of Holmes's meticulous study of Joyce is that, in rebuke (as it were) to Joyce's apologists, it places this prejudice and this super-egotism where they surely belong: at the heart of everything that motivated Joyce to do what he did.

Searching for Lord Haw-Haw is not merely painstakingly researched. It is composed in a lively style that carries the reader effortlessly from first page till last. It is, in short, a scholastic triumph.

Geoffrey Alderman is a historian and journalist