I'm barrucadu, also known in meatspace as Michael Walker.

I read books (mostly sci-fi & fantasy, but I've been getting into history too); I watch anime; I program things for fun (and for work); I play and think about roleplaying games a lot, and sometimes write about them. I write weeknotes, updated every Sunday with what's going on in my life. I used to be into boardgames, but I'm not so much anymore; similarly computer games. I bake acceptable bread. I enjoy listening to metal of all sorts (but casually—don't expect me to converse intelligently on it).
I don't know what else to write here.

You can find me elsewhere on the internet:



I like programming and tinkering with DevOps in my spare time. My go-to languages are Haskell, Python, Rust. I run NixOS on all my machines. I like Configuration as Code and Infrastructure as Code.

You can see all my projects on GitHub. Some favourites are:

In the past I've also served as project leader for Arch Hurd, a GNU/Hurd distribution based on Arch Linux; and worked as one of the first few developers for Uzbl, a Webkit-based web browser.

I also have some Haskell IRC libraries: irc-ctcp, irc-conduit, and irc-client. But these are essentially abandonware right now. If you want to maintain them, get in touch!

Roleplaying Games

My current games of choice are Call of Cthulhu (7th edition), Traveller (Mongoose 2nd edition), and Old School Essentials. I also greatly enjoy Dolmenwood, Delta Green, and ALIEN. I'm not really a fan of storygames, being pretty firmly in the "traditional" and "OSR" camps.

Right now I'm running one regular game, a campaign of The Halls of Arden Vul: the greatest megadungeon ever written.

I also run a TTRPG blog, updated infrequently.


I'm a Senior Software Engineer at GoCardless on the Merchant Engagement team. We have a wide remit covering much of everything that existing customers directly interact with.

Before GoCardless, I worked for the Government Digital Service on GOV.UK.

I like working on tricky technical challenges, and gravitate to infrastructure or backend.

See my CV for a bullet-point highlight reel.


I did a Ph.D at the University of York on the topic of testing concurrent Haskell programs. I ultimately decided that academia wasn't for me, but I'm glad I stuck it out to the end.

Here's a PDF of my thesis.

I published a couple of papers too:

If you want to cite any of those, use this BibTeX:

  author = "Walker, Michael",
  title  = "Revealing Behaviours of Concurrent Functional Programs by Systematic Testing",
  year   = 2018,
My Ph.D thesis.
  author    = "Walker, Michael and Runciman, Colin",
  title     = {{D{'e}j\`{a} Fu}: {A} Concurrency Testing Library for {Haskell}},
  booktitle = "Proceedings of the 8th ACM SIGPLAN Symposium on Haskell",
  series    = "Haskell 2015",
  year      = "2015",
  isbn      = "978-1-4503-3808-0",
  location  = "Vancouver, BC, Canada",
  pages     = "141--152",
  numpages  = "12",
  url       = "http://doi.acm.org/10.1145/2804302.2804306",
  doi       = "10.1145/2804302.2804306",
  acmid     = "2804306",
  publisher = "ACM",
  address   = "New York, NY, USA",
"Déjà Fu: A Concurrency Testing Library for Haskell".
  author    = "Walker, Michael and Runciman, Colin",
  title     = "Cheap Remarks About Concurrent Programs",
  booktitle = "Functional and Logic Programming",
  year      = 2018,
  editor    = "Gallagher, John P. and Sulzmann, Martin",
  series    = "FLOPS 2018",
  pages     = "264-279",
  publisher = "Springer International Publishing",
  isbn      = "978-3-319-90686-7",
  location  = "Nagoya, Japan",
  url       = "https://doi.org/10.1007/978-3-319-90686-7_17",
  doi       = "10.1007/978-3-319-90686-7_17",
"Cheap Remarks About Concurrent Programs".