Older Brompton front brake cable
Your own posted link says


  Brompton with the 10 degree brake levers with an open clevis should be
  replaced with either the 30 degree or new aluminium brake levers.


Sounds like the 10 degree ones risk the cable's mushroom falling out of the open clevis, rendering the brake inoperable.  That would be bad.

You should replace the levers with safer ones.