This summer, we went to Northumberland. The past lies deep over the present there, in this land of far horizons, and over the next few weeks I’ll write a few more entries in this occasional series, the presence of the past.

For today, we’ll look at the well in Bamburgh Castle. The rock on which the presnt-day castle stands has been a stronghold for as long as men have lived in Northumberland. It’s a great lump of Whin Sill, the layer of hard dolerite that extends, mostly underground, through Durham and Northumberland. 295 million years ago, an upflow of magma from the earth’s core was diverted on its path to the surface and, instead of exploding as a volcano, slid sideways, below the surface, spreading out along the fault line between two horizontal layers of rock, rather like the jam in a sandwich. But when the magma cooled, it formed dolerite, a much harder rock than the sandstone that sandwiched it. So, as the softer rock has eroded, the hard protuberances of the Whin Sill have emerged, producing features such as Bamburgh Rock, High Force, and parts of Hadrian’s Wall.

Bamburgh Rock, rising a couple of hundred feet above the surrounding sea and land, is an obvious watchpoint and stronghold. But it lacked one vital feature of a defensible fortress: water. If the defenders were beseiged, they would rely on stored water and catching rainfall – admittedly, not an infrequent occurrence in this part of the world, but, the world being what it is, no doubt drought would be the inevitable partner to siege.

To overcome this deficiency, the Anglo-Saxons dug a well. Through granite. Through 150 feet of granite. And the well is still there, in the lowest level of Bamburgh Castle, with nothing but a small caption to remark this extraordinary feat of Early Medieval engineering.

Here’s me, standing beside the well.

How on earth did they do it?

This is what the caption says:

This Anglo-Saxon well was essential for providing the castle with a reliable and clean source of water. The well is 44 metres in depth and 2 metres in diameter. There are no records about how the well was made but one thought is that fires may have been built on top of the hard whinstone. When the rock was extremely hot, cold water would have been poured onto it causing it to contract and split, making the stone easier to work. Beneath the whinstone is sandstone much softer and easier to excavate.

The sides of the well are smooth and close to the bottom there is an arched tunnel approximately 1.75 metres in height which is reached by iron rungs set into the stone work. Running at a south westerly angle it travels to shrubbery outside the castle near the existing pump house and was made in the 20th century to carry services, out of sight, up to the castle.

So, that is, maybe, how they did it. Hot rock, cold water and hard labour. And, well dug, Bamburgh became well-nigh impregnable, the stronghold which became the base for the Idings take over of the kingdom of Bernicia, the land of the high passes.