a controversial one unfortunately, have used 262/268/272/277/290 in the past and none have come loose after application but (apart from 290) will breakdown due to oil contamination in time and have noticed this on stripping. Loctite 290 is listed as oil tolerant (medium/high strength) and probably your best bet for peace of mind but may need heat to disassemble according to manufacturer notes but i've never had a problem when used with hot oil.
I pity the poor s*d that has to get mine undone - I used 638 - that will not come undone easily without a bit of heat.
The extract from the workshop manual above appears to be from the IE manual. The workshop manual that is readily available online for the carbed SS shows a washer which has to bent as per a tab washer. For some unknown reason the carbed SS parts manual doesn't appear to show the washer or nut in realtion the fitting of the alternator, but they do appear to be under the timing gears section.....shown as a lock washer. However, I think there is a suitable approach to the question asked by the OP. If you don't want the alternator/flywheel to come loose, use Loctite.
Loctite 243 or 270 , 243 medium strength 180 °C 270 high strength 150 °C Don 't know if available in UK