Technical Ducato horn works with no key in ignition

[duntrucking]

Hi

My 2003 Ducato campers horn works when ignition is off. I understand this is normal.

I removed the steering wheel and covers ect to try to find the wire from the horn out off the multi block below steering unit.

The reason for this is to fit an on-off switch on the horn circuit so as I can fit a stoplock with out it sounding the horn as it pushes on it..

Could any one advise maybe the wire colour from the multi-block below the revolving horn track.

Or any ideas as to stopping the horn working with the key removed.

Thanks.