How can you cancel casting a spell?

Question

In combat I often find myself in the situation where I have prepared a spell to be cast, but my follower finishes off the last enemy before I can release it. I usually turn around and fire it off behind me to avoid hitting my follower, which is a bit silly and also wastes magicka.

Is there any way I can cancel the spell?

Answer 1

You can stop casting a spell the same way you un-nock an arrow - simply "sheathing" your weapon (or spell, in this case) will refund the allocated Magicka and not cast the spell.