Info please on Suzuka 1989?

This is not a topic about who's at fault yada yada. We all know the incident.

I was re-watching the race (awesome, remember it like yesterday), and I know Senna was DQ due to ''cutting the chicane'' and not because of a push start. Don't know the regs at the time, but in years since it's been legal to get a push start if you're in a dangerous position, and Senna definitely was.

Now, it has never been explained to me why he was DQ other than he ''cut the chicane'', which on face value, seems ludicrous. What else could he do, go backwards against the traffic?!?

I took a screenshot from the onboard:



On the left hand-side is wall with the letter "OP", it's actually "STOP". I know in races around that era, it was protocol to stop the car if you cut a chicane if there was in fact an escape road (Spa & Hockenheim implemented this 'rule'). Usually there's be a marshall there with a some sort of direction, a flag, a sign etc.

So my question is, is this the reason was Senna was DQ, because he didn't adhere to the STOP signage? If so, then I would have to concede it was a legitimate DQ. Does anyone have any information on this (press conferences, regulations, something)?



Thanks.