DV, you wrote: "The hot air inlet temp of the mixing chamber was above the auto ignition temp, and the mixing chamber is in line with leading edge of the fire"
2 points: use of the mixing chamber (bomb bay heating) was prohibited after the crash. The inlet temp of the chamber would normally have been no more than 100 degrees, as it was sourced from the LP compressor. Although your stated location of the chamber relative to the location of the fire as observed, is correct, the chamber could not have been the source of the fire.
I agree with you that the blow-off valve was not involved in the XV235 incident.
I have written to Tony Blackman explaining where he has made many factual errors in his postulations. He has since replied and stated that he no longer wishes to debate the cause of the accident.
One (last) matter in Tony's postulation that I wish to address concerns the SCP Pre-cooler overheat warning received shortly before the bomb bay warning was activated. Yes, it certainly appears to be a factor in the accident, but it was not. While researching my comments to Tony, I read the transcript of the other in-theatre flight engineer's evidence to the Coroner in which he stated that the SCP Pre-cooler was overheating during the later stages of the AAR. He correctly judged that it was due to a combination of turbulence and high engine power, as outlined within the aircrew manual.
Tony very kindly wrote to me this evening, telling me that H-C's lecture was excellent and that the Nimrod accident was barely mentioned.
Time to let this sad subject go.