Hi prefabsprout (and love the name!!)

Congratulations on the opportunity, you've obviously impressed!!!!
And yes, tell the positve truth about your last job e.g. the job transformed into something you hadn't initially applied for and you felt that you weren't given the opportunity to truely utilise your skills, such as "people skills" whereas the job you're now applying for you feel you can contribute so much more to..............

And SELL YOURSELF!!!!!
I'm sure you can be using lots from when you started at your last job which will apply e.g. conflict resolution, organisational skills, communication skills, team working skills, working on your initiative, responding to difficult/diverse situations..............

And read up as much as possible on the company and job requirements so you're prepared to wow them with you're insight and capabilities in what you're applying for!!!

Of course some things you might not know but if you "wing it" by saying things like "I'm know I'm lacking the knowledge in that area but I'm very motivated in both learning the companies policies and procedures and learning while I'm working. I am a very quick learner"
So keep selling yourself even when you're not sure

As for keeping calm...........maybe see this minimally as a practise in interviewing.........a learning experience for any further interviews (if it weren't to work out)............whatever the outcome it will be a good opportunity.............rather than "you're being put on the spot"............so just try to be yourself. And if during the interview they aren't looking impressed, don't let that faze you/put you off...........it doesn't need to mean that they aren't!!!
Even take a breath and imagine someone you're comfortable with is asking the question and how you might respond to them............
Just take questions, tests, games, "one at a time" instead of worrying about how you may have responded or acted and whether it's good enough..........one at a time............
And if you need to.............between each, silently say in your head something like "I can do this" or "It's alright".............some positive affirmation to yourself................

Just some thoughts.....................

And again..........CONGRATS on the opportunity
It's going to be their loss if it weren't to work out...........but at least you're going to give them the chance to snap you up



Alison