In my experience, the quality of the FDR1 info is dependant on:
1) Obviously the experience and competence of the person completing it
2) The size and importance of the fire i.e. a FDR1 relating to a property fire is much more likely to be accurate than a shed or car fire. Talking of which, I was horrified to read when engineers were planning the Channel Tunnel, one source of data they used to establish probabilities of a vehicle fire in the tunnel and compile procedures was FDR1s originating from car fires. Perhaps not the most reliable souce!! I still occasionally see petrol onto hot manifold as a cause of car fires!!
3) How busy the station has been, say, overnight. If a JO has 4/5 FDR1s to complete (as opposed to 1) they'll be a bit rushed.
If a fire falls within the 3 categories above, it's fair to say a good deal of 'creative investigating' may have been used.
Frankly, School, Hospital and similar 'public interest' buildings are more likely to be investigated and reported efficiently than your average fire in squat bedsit. In London, for instance, it's highly unlikely that a fire in any of those buildings will go unattended by our FI team
I have (rather sadly) enjoyed completing FDR1s and rarely have had any problems. However a fire resulting in 58 'sufferers' which required an urgent FDR1 (as it was debated in the House of Commons 48 hours afterwards) did cause me a few difficulties.
