We first hear of Peter Gillespie in The Cuckoo’s Calling, on the day that Strike splits up with Charlotte and Robin arrives as a temp. Strike is in The Tottenham mulling over his circumstances and financial situation. ‘… if Gillespie called in the loan that had formed the down payment on Strike’s office, Strike would have no alternative but to sleep rough’ (Part 1, Ch 5). Indeed, Gillespie does call the office that day, leaving a message with Robin asking Strike to call him back as soon as possible (Part 1, Ch 6).

When Strike’s sister Lucy calls him at the weekend, she asks Strike if ‘Gillespie is still on your back for repayment’, which he denies. Lucy then suggests applying to the British Legion for help with repaying the loan, which irritates Strike (Part 2, Ch 8).

Gillespie continues to leave messages with Robin, asking Strike to call him back urgently, which he doesn’t do.  Eventually, on a Saturday, Gillespie catches Strike on his mobile, and demands repayment of the loan. Strike asks him ‘Got you working weekends now, has he?’ and we learn that Gillespie works for Strike’s father, rock star Jonny Rokeby, and that it is Rokeby who has loaned Strike the money to set up the agency.  Strike tells Gillespie that he will send a repayment soon, and to ‘get off my fucking back’  (Part 4, Ch 4).

At the end of the book, after the case has been solved, we hear Robin answer the phone to Gillespie.  She informs him that there is a cheque in the post for ‘all the arrears … and a little bit more’. We can infer from what she says that Rokeby has offered to forgive the loan, but Strike is adamant he wants to repay it in full (Epilogue).

Gillespie’s name then doesn’t come up again until the fifth book of the series, Troubled Blood. Strike’s brother Al calls him to try and persuade him to attend a party that their father is holding. Strike declines, and says that Rokeby had, amongst other things, set his lawyers on him, chasing him for money that was legally his.  Al responds by saying that Rokeby didn’t know how heavy Gillespie was getting with Strike, and that anyway Gillespie had now retired (Ch 34). 

Some time later, Strike and Robin are talking in the office and Strike tells her the story of the second and last time he met his father. They met at Rokeby’s manager’s office, and Rokeby ‘was there with his long-time lawyer, Peter Gillespie.’ Robin is shocked to hear that Strike’s father had loaned him the money, as she remembered how aggressively Gillespie had chased Strike for repayment (Ch 58).

Strike tells her Gillespie’s ‘whole ego was invested in being my father’s enforcer’ and that ‘the bastard was half in love with my old man, or with his fame’. Strike’s attitude toward his father and Gillespie angered Gillespie, who then insisted on upholding the loan agreement ‘to punish me for telling him exactly what I thought of the pair of them’ (Ch 58).