But however thick the veil, nothing could withstand the searchlight of official scrutiny. In 1921, The Link's founder Alfred Barrett was found guilty of corrupting public morals and sentenced to two years' imprisonment with hard labour. In his summing-up, the judge expressed his deep regret that this was the maximum sentence open to him. Penal servitude, he felt, would have been a much more attractive - and appropriate - option.

Yet even the threat of breaking rocks was not enough to discourage a host of new publications. Nor were persistent rumours that they were a front for White Slavers - swarthy Levantines and the like who would coerce innocent girls into acts of unspeakable degradation. Throughout the '20s, contacts magazines continued to thrive, providing what George Orwell called "a guide to the mysteries of the collective unconscious".

H. G. Cocks, one suspects, has taken Orwell's remark a bit too much to heart. As he writes in his introduction, the stories contained in the personal ads "tell an oblique history of British morals in the 20th century". In order to lend weight to this theory, he uses the ads as pretexts for examining various topics: sexual behaviour, marriage, pornography and so on. He clearly knows his stuff and he certainly is thorough, but he's also - given the nature of the subject-matter - rather more po-faced, more academic, than necessary.

Things get much more interesting - and fun - when he sticks closely to his "secret history", tracing how the personal column has moved from being the preserve of the desperate and the depraved to its present, rather dreary, respectability. As always with any great sea-change in British life, one can never underestimate the role of class as the catalyst.