Emergency key.

[Tanglewood]

S500 dead battery Reserve key with WD40 turns boot lock but boot fails to open.

 

[Tanglewood]

Reserve key with WD40 turns boot bock but boot fails to open.

 

[Tanglewood]

S500 emergency key and WD40. Key turns boot lock. Boot fails to open.

 

[KennyN]

Does the reserve key not open the drivers door ?

If it does this should let you open the bonnet and put a power supply onto the jump start points , or at least pop the boot from inside the vehicle.

K

 

[mioba]

the only flaw of the W220 is there are no jump points in the engine bay. It is direct to battery only - in the boot.
The other way is to get under the car and put cables on the starter.

 

[brandwooddixon]

Do you have a power close boot? Did you try lifting the boot to open it once unlocked?

Otherwise, get the bonnet open and apply power to the main battery feed into the fuse box on the left side of the engine bay. You can also pick one of the positive side of the largest fuses. This should give you enough power to cycle the central locking and power the boot open.

Note, sometimes you need to repeatedly pull on the door handle when unlocking the drivers door to pop the lock fully open.