Hmmm, well it was only an M4x8 Caphead, but it does appear to have gone through.
The washing-up liquid test shows very slight seepage when removed, but as yet no noticable drop in pressure as measured with a tyre pressure gauge, so at least it's not truly running flat.
Our stock/stores guy will be in the carpark with a broom tomorrow, he just doesn't know it yet.
