Consistency of user experience
Wherever possible we should use the same language and the same design patterns. Our aim is for users to interact with information and services, without being aware of the range of technology in the background.
Sometimes this won't be possible, but we will make sure our underlying approach is consistent. So our users will have a reasonable chance of guessing what they’re supposed to do.
This isn’t a straitjacket or a rule book. We can’t build great services by rote. We can’t imagine every scenario and write rules for it. Every circumstance is different and should be addressed on its own terms. What unites things, therefore, should be a consistent approach — one that users will hopefully come to understand and trust — even as we move into new digital spaces.
We are designing informational and transactional services that meet user needs. No more, no less.