First a little explanation for anyone who's not really clear what twin
leading shoes do:

In drum brakes, the "leading" shoes provide much more braking than the
"trailing" shoes. Rear drum brakes have one leading and one trailing so
the handbrake will hold facing uphill or downhill. Front brakes with
twin leading shoes provide much better braking going forwards, at the
expense of braking performance going backwards - who needs to stop from
50mph backwards anyway?

Now my story of woe:

My ex's Mini convertible which I've mentioned here occasionally had 1970
era twin leading shoe front drum brakes. My parents had a *very* steep
driveway up the side of a steep hill, complete with a sharp bend and
some very fine loose gravel on the bitumen surface.

One day I had to stop part way up the driveway, when something or
someone at the top was in the way. I could not stand on the brake pedal
hard enough to hold the car on the slope. The rear wheels were locking,
and sliding towards the edge of the drive, even as the front wheels
still rolled, leaving me sliding down the hill out of control. I sort of
slithered and rolled mostly out of control back down the driveway,
managing not to run off the edge, and thankfully no one was coming down
the street, because I certainly couldn't have stopped.

But the front brakes didn't lock.....

Apparently twin leading shoes were second generation of antilock brakes?

More like anti brake brakes....:-)