Before the first light will be as the top of the diagram.Thank you again.
I haven’t quite decided where to position the PIR but it would be somewhere on the fence either just before the first new light or possibly between the last 2 lights as this would be close to the gate that leads to the garden and the likely point of access for an intruder. Obviously wouldn’t position it towards the house/ bifold as we could constantly knock it off whilst using that room.
If between the last two, you will need four core cable so the power goes to the PIR and then the Switched Live goes back to the previous lights.
The PIR switch will have to be left ON for it to work.