BOAC .. gradient suggested was for the -300.
Interestingly, I can't recall ever having had to dirty up at height in the 727-100/-200 to get down in normal ops.
Reasonably frequent need in the 737 if ATC had to hold you high back at 40-50 miles or so and then forgot about you for a while ...
Slow down to max flap speed in anticipation, dirty up on further descent clearance, go down, final slow down and into the slot .. worked very fine and was quite predictable.
One needed to factor in the wind, of course, and the mental arithmetic on a very long extremely tight straight in ILS saw steam coming out of the ears on the way down ... DME was king of the calculation inputs .. only very occasionally did one get caught out close in and still have to do an orbit or miss.
I recall one approach SY 16 ILS where we were still up near FL200 after coming around the corner at MQD onto the runway extended centreline .. and ATC just kept us there ... with a fairly high traffic density... lots of mental arithmetic until in the slot on the ILS but it worked out just fine.
Flap 25 was the most we were permitted to use without spinning up. Can't get that certification engineering hat off .. approach referring to last before land.
I was never really interested in ROD while poling (other than as a normal I/F scan input) unless the clearance required something specific .. it was all about gradient capability against requirement to end up wherever I needed to end up ...
Of course, I routinely ignored the FMS so still had enough grey matter in reserve to run the mental calcs .. had I tried to factor in the lies the box told about descent back in those days it would have been a foregone waste of time trying to make a tight descent requirement ....