The claim relates specifically to the spine 2 project, and is as measured over the 5 years since it went live. There are a lot of systems which depend on Spine 2 for their own availability, it is not the sort of thing that can go down at any time without a lot of people noticing.

I'm biased in that I've been heavily involved in the project, but I will stand by the five years of five nines availability claim.

My NHS trust doesn't even use Spine 2. That would require reliable Internet.

The lead engineer/designer on the project makes this claim in these slides. I don't know whether this gives the claim more veracity in your eyes, but it's there.

[1]: http://martinsumner.github.io/presentations/spine2_erlang#/2...