In the 1840s, he observed, documented and described the state of working people in London for a series of articles in a newspaper, the Morning Chronicle, which were later compiled into book form.

Mayhew went into deep, almost pedantic detail concerning the trades, habits, religion and domestic arrangements of the thousands of people working the streets of the city.

For instance, Jack Black talks about his job as "rat and mole destroyer to Her Majesty" and remains in good humour despite his experience of a succession of near-fatal infections from bites.

[1] Beyond that anecdotal material, Mayhew's articles are particularly notable for attempting to justify numerical estimates with other information, such as census data and police statistics.

A fourth "Extra Volume", published in 1861, was co-written with Bracebridge Hemyng, John Binny and Andrew Halliday and covered the lives of streetwalkers, thieves and beggars, but it departed from the interview format to take a more general and statistical approach to its subject.

Alongside these relatively familiar forms of trade in consumer goods and services, Mayhew's work describes lesser-known trades driven by now-obsolete markets and by sheer poverty, such as gathering of snails for food, and the extreme forms of recycling practised by pure finders (who collected dog dung for tanneries), the scavenging of the mudlarks (who spent their days combing the shores of the Thames for valuables hidden in the sand and silt) and 'toshers' (who searched the sewers for scrap metal and other valuables).

The housewife in her thick shawl, with the market-basket on her arm, walks slowly on, stopping now to look at the stall of caps, and now to cheapen a bunch of greens.

Little boys, holding three or four onions in their hand, creep between the people, wriggling their way through every interstice, and asking for custom in whining tones, as if seeking charity.

Mayhew interviewed everyone — beggars, street-entertainers (such as Punch and Judy men), market traders, prostitutes, labourers, sweatshop workers, even down to the "mudlarks" who searched the stinking mud on the banks of the River Thames for wood, metal, rope and coal from passing ships, and the "pure-finders" who gathered dog faeces to sell to tanners.

Writer Ben Gwalchmai was inspired to write his satirical novel Purefinder after reading about pure finders in the works of Dickens and Mayhew.

[citation needed] In 1953, the articles, which were written by Alex Atkinson and illustrated by Ronald Searle, were published in a single volume under the title The Big City or the New Mayhew.