"Oranges and lemons", say the bells of St. Clement's
"You owe me three farthings", say the bells of St. Martin's
"When will you pay me?" say the bells of Old Bailey
"When I grow rich", say the bells of Shoreditch

Comrades, 'ave ya noted that so far in yer novel Mr. C can only remember the first coupla lines of the nursery rhyme? We'll learn more and more as the story goes on.
'Ere's the 'istory: In 1783 the infamous public execution gallows in London was moved from Tyburn-gate (Marble Arch) to Newgate, a notorious prison for both criminals and debtors (hence "When will you pay me"?). This move was necessary to reduce problems caused by the crowds, often exceeding 100,000, gathered along the execution procession route. The picture at the top of this post shows the gatherings. At the toll of each of the church's bells, another person would be executed. Nice, 'eh?

Those who understand foreshadowing may be curious to find the rest of the lyrics, eh?