Suppose a Royal Mail worker knocks on the door to deliver a parcel which needs to be signed for. No one is home. He is supposed to leave a "Something for you" card and bring the parcel to the collection point. Or attempt again the next day.
Instead, the postman signs for the delivery himself, trying to make it appear like signed by the recipient, and leaves the parcel at the door.
This conduct would of course break Royal Mail's internal policies and procedures, but would it also break any laws?
If it matters, let's assume the parcel was later found by the recipient safe and sound.