Digging through the plough soil superposited on the Vindolanda forts you learn to spot certain colours and materials – the terracotta of pottery, the green of copper alloys, the orange of rusted iron...
In our excavations we come across iron nails of all shapes and sizes. I say "shapes" – I was very excited to have unearthed a Roman ring, only for the Director of Excavations to decide it was a nail bent into a circle. Pissing in my Cheerios indeed.
The bigger nails are humorously referred to as "Jesus Nails". Interestingly, they can be the right length for crucifixions (5–7"), but Constantine I outlawed the practice in the early 4thC, and we're excavating a fort built in 370AD.
However, when we excavate the earlier forts, is there a chance there could be crucifixion nails? Crucifixion was a way of life (well, death) across the Empire - but there's very little archaeological evidence for specific instances of it. And as Romans used nails for everything you'd pretty much have to find one stuck in someone's foot in order to prove it's actually a "Jesus Nail".
Were there crucifixions in Britain? Yes! Tacitus' Annals specifically mention Boudica crucified Romans.
neque enim capere aut venundare aliudve quod belli commercium, sed caedes patibula ignes cruces...
For it was not on making prisoners and selling them, or on any of the barter of war, that the enemy was bent, but on slaughter, on the gibbet, the fire and the cross...
Tactitus Annals XIV.33
Romans used capital punishment very publicly to assert their control and subdue the locals. Boudica may have been inspired to copy the practices of her oppressors.
She was hard as nails.