Engine won't switch off.

[Dartboard1]

Hi guys,My 2014 mark 2 c4 picasso won't switch off after I park up remove the key fob and press the button.At the moment I am having to deliberately stall the car to stop engine disconnect the battery to turn off lights, radio etc and then reconnect battery to lock the car.It will then start ok but I have to Go through this ritual every time I want to park it.you guys and really clever and I'm hoping you can help with this strange one.
Thanks in advance.

[PaulC5]

If a diesel check the oil level is not high in case it is running off the oil in the sump.

[xantia_v6]

To narrow things down a little, tell us which model of engine you have.

It is probably easiest to have the car checked on a good diagnosis machine, as there should be some fault codes, and live data should show what circuits are unexpectedly energised.

[Dartboard1]

It's a diesel ok,1.6hdi,oil levels grand.
Vin VF7**************[VIN obfuscated, can be read by forum staff].
Thank you

[wheeler]

I would disconnect all the connectors on the under bonnet fusebox & check for any signs of water ingress.
When you try to switch it off does the dash go out or does the dash stay illuminate?
When you reconnect the battery does all the ignition lights come straight on without even putting the key in of does it all behave as normal again until you try to switch it off?

[Dustysweeper]

Press and hold the ignition switch for around 20 seconds, it should shut off.