Position a mortice deadlock about halfway up the door and fit a night latch on your front door one third of the way down.
Fitting a mortice lock to a rebated door.
Mortice latch or tubular door latch showing the latch casing the catch and door handle spindle insert.
To install this lock see section 4 below.
A mortice mortise deadlock is a strong form of lock that is embedded within a cut out pocket space inside the door or furniture structure as well as having external components.
If you want to fit one yourself you ll need to be capable of woodworking as well as using the tools required to fit the lock.
The second important part of this how to is to buy a rebate kit.
The fitting instructions supplied with a mortice lock will normally specify the thickness of door it is designed for problems will arise if a mortice lock is fitted to a door thinner than it is designed for.
Unlike a normal door where you would fully recess the latch into the door and it would close against a frame with a rebated double door like ours the latch actually needs to sit partly out from being fully inside the door.
Easy to follow instructional video on how to install a mortice lock in rebated double timber doors.