"My 'O' Level grade 3 maths wasn't much use then."

Obviously not!

As a totsl aside the threat to ban the UK from Irish airspace is a bit of a joke. From the Journal IE:

"When last year Russian bomber aircraft – one reportedly carrying an inert nuclear device – entered Irish controlled airspace with transponders switched off, these aircraft were intercepted by RAF fighter planes and shadowed as they probed our ‘air defences’ and reaction times.

With no primary radar to speak of and no Irish Air Corps aircraft capable of meaningfully intercepting or shadowing such intruders, our airspace is undefended and unmonitored.

The Russians have clearly identified Irish airspace as Europe’s weakest link in terms of surveillance and defence capability. Let’s hope terrorists, intent on hitting American, British, French and other European civil aviation targets have not reached the same conclusion.

Therefore we rely on Britain and the RAF to provide security in our skies. So far the deal sounds sensible, however unpalatable, given our lack of infrastructure and capability."