Why we (I) chock the wheels.

Today whilst attending the NRMA Motorfest in Sydney, the following happened.
Parked facing East in Bent St. Slight uphill gradient. Thought I would polish the roof of the cab before the multitude arrives. Opened the drivers door and placed both feet on floor of cab whilst standing upright outside the cab, with rag and polish in hand.
As soon as I placed my left foot down, I heard a click, followed immediately by a loud whoooosh.
Like in the cartoons, I realized what I had done and by the time I had blinked the old girl had rolled back onto the chock.
Yes. I had just released the parking brake >
Nobody But I Knew what I had done. But as I believe we can all learn from others mistakes, I bare my soul :. Rod.

What sort of vehicle is it, where is the park brake located ?
I was once getting out of a 1422 Benz when the strap on my bag caught the park brake handle on the dash and released it, fortunately just rolled a few feet into the gutter.

A B61 where the park brake control is a little "T handle" placed on the floor just under the right hand edge of the drivers seat, ie about 4" in from the door.