Next year we shall commemorate the centenary of the outbreak of the First World War. When Britain declared war on Germany scenes of jubilation were seen throughout the UK. But as the war dragged on, and as British casualty lists climbed to obscene levels, violent anti-German hysteria, cynically exploited by politicians, gripped the nation.

This madness affected British Jews in a number of ways. Anyone with a foreign-sounding name became an object of suspicion. Anyone educated in Germany could expect to be hounded from his employment. Anyone born in Germany was regarded, prima facie, as a traitor who was expected to somehow prove his innocence. Prominent Jews of German birth were challenged to write "loyalty" letters to The Times. Targets of these campaigns included the laryngologist Sir Felix Semon, and the industrialist Sir Edgar Speyer.

The case of Speyer is particularly tragic. Although born in Frankfurt he had come to London as a young man and was naturalised in due course. The electrified underground railway system Londoners now enjoy was in some respects his creation.

But he was also a patron of the arts (including the Whitechapel Gallery) and rescued from virtual bankruptcy that quintessentially English extravaganza, the Promenade Concerts. He also funded Captain Scott's Antarctic expeditions. Created a baronet in 1906, he was sworn in to the Privy Council three years later. But all these good works counted for nothing once war began. The Speyers were ostracised and - in effect - driven out. In 1921 his naturalisation and that of his wife and daughters were revoked.

Lentin tells the story in a way that is sympathetic, but grounded in the sources. Some of the accusations against Speyer were clearly nonsensical. But in some respects, for all his sound business judgment, he was his own worst enemy - he continued to maintain personal and business contacts with Germany whilestill a British citizen, though living in the then neutral United States, and he continued - albeit indirectly - to trade with the German state.

His characterisation of these as merely "trivial" offences betrays a certain naivety, or perhaps cynicism. Lentin is surely right, however, to position Speyer's fate as, at least in part, an outcome of his friendship with Asquith, the prime minister who blundered the country into a war he proved tragically incapable of waging.