How do you dig a Siege Tunnel?

I was twelve when I first went down the siege tunnel at St Andrews Castle. It was scary and, if you are at all claustrophobic, it’s definitely not for you.

For, the first part you bend double, creeping down the central trench, at risk of scraping  your back on the rough stone above.

The Counter-Mine and narrow entrance to the siege tunnel

Then suddenly the passage ends in a wall of rock. There is a narrow, jagged hole beneath you.  Do you dare squeeze yourself though it and descend the metal ladder to find out what’s below?

Down you go and the space opens out. The tunnel is a tale of two halves and this part is broad and high with steps leading to the sealed off entrance, which is beneath a house in North Street.  There’s also a grating visible, which my brother and his friends entertained themselves during school lunchbreaks by howling  down into, from the street above, to terrify (or perhaps create atmosphere for) the visiting American tourists creeping around below.

Where the mine was begun, the entrance now sealed off beneath a house in North Street

I have so far called this ‘a tunnel’ and was always baffled as to why it was referred to as ‘a mine.’ When I was researching The Castilians I finally understood. Here’s an extract where Will discovers what the tunnelling/mining is about …

Will works away clearing rubble but puzzling over what they’re doing.

‘Why do we not wait for our attackers to break through and then pick them off as they emerge? Then we would not have to expend effort digging, and surely it is better than both attackers and defenders meeting underground,’ he whispers to an equally baffled Nydie.

‘It would not,’ sighs Lee who has overheard them…

‘Arran’s intent is not to gain entry. The purpose of a siege tunnel is to undermine the castle defences and that is why we call it a mine. Our attackers will begin at a safe distance from the castle so they cannot be seen or fired upon, which is how we cannot yet be sure they are digging.’

‘How will it cause the castle walls to collapse, unless they mine close beneath the surface?’ Nydie asks.

‘No, that would not be wise – else they would find themselves buried alive if the wall collapsed unexpectedly. Once they believe themselves to be underneath the castle walls they’ll hollow out an area, which is supported by timber props to keep those digging safe, until all is ready. Then explosives will be laid and fires set below each prop and, when the miners are confident the fire has taken hold, they’ll flee out of the mine to safety. The conflagration will cause the tunnel to cave in and, if they’ve done their work well, the defensive wall above the tunnel will tumble down and our besiegers can take the castle.’ 

The ladder linking the two halves, and the mine built on a larger scale to set explosives beneath the curtain wall

The mine and counter-mine at St Andrews Castle have been dug through rock, which is remarkable — and why it’s still there after nearly five hundred years. It’s also the best surviving example of siege tunnelling in Europe, from that period.

I still wonder at the amazing feat to dig, and dig so fast. There’s little reference to it in the papers of the time. The French ambassador to the English Court mentions the mine and counter-mine in his letters of November 1546, but by December it’s over and the attempt to break the siege has failed again…

They hear sounds of alarm; it seems they are discovered. Any attempt to stay quiet is given up and they excavate as hard and fast as they can. Someone has fetched Richard Lee and he squeezes past Will, directing them to attack the ground beneath, and not before them.

‘We must be quick,’ he hisses, ‘else they’ll have time to set explosives and blow us into eternity.’

Will shovels the rubble behind him to keep the area clear for the miners to work – there’s no time to scuttle back up the passageway with it now. A hole has appeared in the floor of the tunnel. Lee has a man shield the candles, whispering that he needs it dark to see if there’s torchlight shining through from below.

Will, Lee and the two miners all squeezed tight together nudge one another: light is shining through. They enlarge the hole, cries beneath them growing loud, then fading. Lee kneels at the edge, and sticks his head through. Will can feel Lee’s body tense, ready to jerk his head out if necessary. He is a brave man. They wait.

Lee lifts his head out and smiles. ‘It could not be more perfect.’

If you’re ever in St Andrews Castle, don’t forget to see the mine and counter-mine. It’s one of the most atmospheric places you’ll ever visit. And in answer to the question, how do you dig a siege tunnel…it’s backbreaking work mostly using  a  pick-axe, partly because the besiegers are trying to attack without those inside the castle knowing.

frontage of the ruin of St Andrews Castle
Castle frontage and the dry moat, where the entrance to the mine can be found