There is a theory that Shakespeare was an accountant. How else to explain the detailed use of bookkeeping metaphors in his writing? “We shall not spend a large expense of time/ Before we reckon with your several loves,” declares Malcolm in Macbeth, “And make us even with you.” The jailer in Cymbeline compares the hangman’s noose with an accountant reckoning the credits and debits of the condemned man’s life. And The Comedy of Errors refers to a debt as a “thousand marks”, a unit only used by book-keepers in Elizabethan England.

Yet Shakespeare seems to have been rather loose with his economics. Rob Eastaway’s new Shakespearean mathematical miscellany, Much Ado About Numbers, tells us that Shakespeare put Dutch guilders in Anatolia in The Comedy of Errors, situated Italian chequins in Phoenicia in Pericles, described Portuguese crusadoes in Venice in Othello and had Julius Caesar’s will bequeathing Greek drachmas to every Roman.

There is something to be learnt from Shakespeare’s attitude to numbers (besides that he’s a poor guide to foreign exchange markets). As Eastaway explains, Shakespeare’s works are richly adorned with numbers. Hamlet’s “thousand natural shocks/ That flesh is heir to” is just one of more than 300 instances of the word “thousand” in Shakespeare’s work.