IIRC, the Invicars had a front wheel that turned nearly, or maybe through? 360 degrees, so you could spin them on the spot. A couple of my mates had the Reliant 3 wheelers that you could drive on a motorcycle licence before you passed your car test. One guy had a 3 wheel truck he used to do building and tree work with, we used to sit in the open back and freeze our nuts off going to the pub in winter.
I lived in Thundersley, so saw a few of the Invicars about, they had interesting controls, maybe custom for each user - good idea, but why they made them a 3 wheeler, God only knows?