Most people think a mortice lock and a lever lock are the same thing, but they are different - a mortice is the style of lock and a lever is the system. However, you can have a mortice lever lock.
The lever lock works by using a bitted key that moves each lever to a specific height, this pushes the locking bolt into the metal boxed strike plate that sits in the frame of the door. This style of lock is exceedingly difficult to break as it secures into the door frame.
The more levers the lock has the more secure the lock is, three-lever, five-lever, seven-lever and more.
Most insurance companies want you to fit a five-lever mortice lock with a BS heart-shaped Kitemark that meets the BS 3621 standard, otherwise, they will request a higher premium.
A five-lever mortice lock with a BS 3621 standard is considered one of the best locks for a front door.