Petrol floats on diesel, so fingers crossed

Except that in the JTDs fuel is circulated to the engine and back to
the tank in a similar way to petrol injection systems so the fuel will
be fairly well mixed now. One of the benefits of this is a self
bleeding low pressure diesel fuel system which is a joy if you have to
open it up (for example to replace the water trap). There's an
electric lift pump in the tank as well as the high pressure pump at
the engine end. I've never heard the lift pump being activated by the
door locks as part of some fancy pre-flight start up though - maybe
that's a German thing. Also, if it was activated, you wouldn't perhaps
need to crank the engine to bleed the fuel system. It takes 5-10s of
cranking to get fuel from the tank to the engine.

Certainly. However, my understanding is that, diesels may cope with a
small amount of petrol. I've heard of lorry drivers using 10% petrol
in their diesel in the coldest of winters.

I don't think luck will play much part here - if there's enough diesel
to maintain lubrication over the petrol's cleaning abilities, you'll
come through. If not.... My understanding is that it's the high
pressure diesel pump that gets damaged if anything does but it's eye
wateringly expensive nevertheless.