PEUGEOT 508 Handbook page 66

Access
Locking/ unlocking from the inside
F Press the button.
this allows the doors and the boot to be locked
or unlocked.
After unlocking, if no door is opened
within 30 seconds, the doors lock again
automatically.
64
Automatic central locking of the
doors
the doors can lock automatically while driving
(speed above 6 mph (10 km/h)).
to activate or deactivate this function, press
and hold the button until a message appears in
the screen.
Driving with the doors locked may make
access to the passenger compartment
by the emergency services more
difficult in an emergency.
If the vehicle is deadlocked or locked
with the remote control or the door
handles, the button is not active. In this
case, use the key or the remote control
to unlock.
When carrying large objects with the
boot open, you can press this button to
lock just the doors.
When locking from inside, the door
mirrors do not fold.