7 May 2023: J.K. Rowling revealed in a reply to someone on Twitter that she had started writing the eighth Strike book and that she had spent six hours of solid work on it that day.

That's a very lovely thing read after six hours solid work on Strike 8!

— J.K. Rowling (@jk_rowling) May 7, 2023

31 January 2024: Rowling updated her Twitter/X header to a photo of the coat of arms above the entrance of the Freemason’s Hall, London. This was her first Strike 8 header.

16 February 2024: J.K. Rowling changed her Twitter/X header photo to La Coupee on the island of Sark in the Channel Islands.

21 February 2024: J.K. Rowling finished writing Part 6 of the book.

I finished part six an hour ago.

— J.K. Rowling (@jk_rowling) February 21, 2024

15 March 2024: J.K. Rowling tweeted from the island of Sark confirming that the title of Strike 8 is The Hallmarked Man.

The following day, she changed her Twitter/X header to a picture of a detail from an English hallmarked sterling silver neff sailing ship.

In another tweet, she confirmed that ‘a few chapters’ of the book would be set on Sark. She also gave emoji clues to the plot of The Hallmarked Man:

3 April 2024: J.K. Rowling mentioned on Twitter/X that she was writing a chapter that features Strike and Robin in a cold and rainy London in February; specifically Cricklewood.

7 April 2024: J.K. Rowling updated her Twitter/X header to a picture of Crieff, Perthshire, Scotland.

14 April 2024: As the StrikeFans team were visiting London, we asked J.K. Rowling if she could let us know a pub from The Hallmarked Man. She replied with The Prince of Wales on Drury Lane.

15 April 2024: J.K. Rowling revealed that the song Silver Bells by Dean Martin is mentioned in The Hallmarked Man.

28 April 2024:  J.K. Rowling replied to a tweet letting us know that Strike and Robin were currently in February 2017, Strike in a bar and Robin at home.

16 May 2024:  J.K. Rowling posted a picture of the epigraph for Part Seven of The Hallmarked Man on Twitter/X.  It is a quote from a novel called A Maid of the Silver Sea by John Oxenham.

She then went on to reveal that she was using five different sources for the epigraphs in The Hallmarked Man.

31 May 2024: J.K. Rowling updated her Twitter/X header to a photo of the Iron Bridge in Ironbridge, Shropshire.

3 June 2024: In replying to someone on Twitter/X, J.K. Rowling revealed that Strike goes to The Falcon pub at Clapham Junction.

7 June 2024: J.K. Rowling said she was on Chapter 102 of the book.

9 June 2024: Rowling revealed that The Swan Taphouse in Ironbridge was to feature.

12 June 2024: J.K. Rowling revealed on Twitter/X that lyrics from the song Tous Les Garçons Et Les Filles by Françoise Hardy will appear in the novel.

I was really sad to hear Francoise Hardy's died. I loved her songs and she was beautiful and fascinating. Her memoir, 'The Despair of Monkeys and Other Trifles', is wonderful and, by total coincidence, there are lines of her lyrics in the novel I'm currently writing (Tous Les… https://t.co/jsFunA2LIJ

— J.K. Rowling (@jk_rowling) June 12, 2024

16 June 2024: J.K. Rowling updated her Twitter/X header photo to one of the red lift in The Savoy, London.

21 June 2024: J.K. Rowling posted that The Hallmarked Man was ‘going very well’ and that she was writing Chapter 106.

27 June 2024: J.K. Rowling updated her twitter header to God’s Own Junkyard, Walthamstow, East London.

4 August 2024: J.K. Rowling updated her twitter header to a quote from The Golden Journey to Samarkand by James Elroy Flecker.

29 August 2024: J.K. Rowling tweeted that she had been working on The Hallmarked Man during a holiday to Greenland. She posted a photograph of the epigraph to Part Nine of the book which is another quote from The Maid of the Silver Sea by John Oxenham.

22 September 2024: J.K. Rowling posted that she had spent nine hours working on ‘a particularly good bit’ of Strike 8. She went on to say that ‘there’s nothing like writing an encounter you’ve foreshadowed for years’. She then confirmed that she was writing Chapter 119.

28 September 2024: J.K. Rowling updated her twitter/X header to picture of a blue oranda, a type of ornamental goldfish.

11 October 2024: J.K. Rowling updated her twitter/X header to a picture of a swan:

23 November 2024: On Strike’s 50th birthday, J.K. Rowling reported that The Hallmarked Man was very close to completion:

1 December 2024: J.K. Rowling changed her twitter/X header to a picture of Wild Court in London:

17 December 2024: J.K. Rowling confirmed that she has finished writing The Hallmarked Man:

20 December 2024: J.K. Rowling replied to someone about finishing the eighth book.

26 December 2025: J.K. Rowling said her husband Neil was half way through reading the manuscript.

28 December 2025: JKR said book 9 is begun!

23 May 2025: The book cover was revealed on Apple Books US.

J.K. Rowling also updated her Twitter/X header of a photo of The Hallmarked Man title from the book cover.

28 May 2025: The book blurb was released.