NServiceBus error "Parameter name: meth"

It's been a while since I used NServiceBus and I got this annoyingly cryptic error message this morning:

Value cannot be null.
Parameter name: meth

I finally found this post about it and it's actually a fairly obvious mistake - I had added property without a setter on one of the objects that needed to be serialized as part of my message. The error message was unfortunately cryptic enough for me to take a while to find it. I thought I'd post this on here for my own future reference.

HTTP Pre-Authentication

Rick Strahl posted this excellent article on pre-authenticating HTTP requests - this is something that's caught me in the past but he explains the whole concept so well here I thought this was worth noting for my own future reference.