Gapster, smudger, Helen 49 etc. Lots of talk of minimum police etc, and how ATC should not be the arbiters of when to make approaches etc. Now, granted I am only looking here at CAP 413 and not the ANO etc, but Chapter 4, page 44 of the current edition (19) has exactly the scenario in question (sorry about lack of formatting):
In the UK, there is an approach ban which states that a pilot may not continue an
instrument approach beyond the outer marker or equivalent position, if the reported
RVR, or at aerodromes where RVR measurements are not taken or available, the
visibility, is below the minimum specified for that approach. Essentially, this means
that a pilot may not descend below 1,000 feet above the aerodrome when these
conditions exist. This RVR/visibility is known as an 'absolute minimum'.
7.3.9 Should a pilot indicate that he or she intends to commence an instrument approach
when the reported RVR/visibility is less than the notified 'absolute minimum' value,
the controller should inform the pilot using the following RTF phraseology:
7.3.10 If the pilot states that he still intends to continue the approach below 1000 ft above
aerodrome level, the controller shall inform the pilot.
7.3.11 This shall be followed at the appropriate times by the following transmissions.
BIGJET 347, RVR runway 27, 650
600 600 metres
BIGJET 347
BIGJET 347, RVR runway 27,
touchdown not available, mid point
650, stop end 550 metres
BIGJET 347
BIGJET 347, you are advised that the
current RVR/visibility is (number)
metres which is below the absolute
minimum for a (name) approach to
runway (number). What are your
intentions?
BIGJET 347, if you continue the
approach and descend below 1000
feet above aerodrome level, it is
believed that you will be
contravening UK legislation and I
shall be required to report the facts.
Acknowledge
BIGJET 347, there is no known
traffic to affect you making a (name)
approach to runway 30
BIGJET 347, there is no known
traffic to affect you landing, surface
wind 280 degrees 16 knots
I assume this does not apply in Ireland but, as I stated before, it might well have had some bearing on the final outcome i.e. I assume these guys thought they could get away with making wildly illegal approaches; if it was clear that they would not, I think it more likely they would have diverted or not set off in the first place.