Benchmark

This should be A1000 or Z9999 because it is so important but it is just S1537.
It's on the trig point at the summit of Scafell Pike - England's highest mountain, but then you all knew that didn't you.
Checking the BM number ensured we were on the correct mountain and hadn't taken a wrong path in the mist, but then the 200 odd people milling around in the fog (including a tuba player) couldn't all have been lost.

BTW this is a Boeing Blip - 767.
I wonder if we should do Peugeot and BMW Blips too?