Introducing Inspector Henry Peckover of Scotland Yard's fraud squad, an undeniably distinctive fellow: he talks pure Cockney but writes poems for The Listener that read like jazzy blendings of Betjeman and Eliot. His debut case: when a tart called Dawn de Nuit is ""bashed to blazes,"" her roster of clients is found to include Sheik Mohammed Zadiq, a key figure in a government construction fraud scheme that Peckover has been investigating. So Henry, though always true to his cozy mate Miriam, mingles with tarts as well as bluebloods--the dialects and local colorations keep shifting--as the frustrating trail leads to. . . Henry's Scotland Yard boss and some sexual jealousies. American readers will have to work a bit at following the references and feeling the milieus, but Kenyon's London is roughly vivid enough and Henry has enough intriguing potential to justify a little extra patience and application.