The secrets of slate

Nigel Smith in the mine founded by his father, Claude.

It’s 1am. I've only met Nigel twice and I really want to send him a message. I hold out for another seven hours and pick up my phone. I drop the formalities. “In theory”, I type "could there be Collyweston slate under my house?" He replies: “Sounds like we've got competition.”  Living less than two miles from Claude N Smith, the Collyweston slate mine, my question is quite a reasonable one but without applying to open a mine, I’m unlikely to find out. The mine was founded by Claude in 1965 and, in 2016 Nigel and his wife Viv reopened the mine following Claude’s retirement. Visiting the mine some months before was an easy commute, bumping over the field on my bike, passing the rock that looks like a wild dog and the toppling, lichen-covered dry-stone wall, the cement works in the distance. And I’m there. Collyweston stone is a sedimentary fissile oolitic limestone formed in the Jurassic period and in the office there’s a fossil dating back to the Bajocian age – known as a water spider, its official name is Phyllochilus bentleyi which I’ve struggled to type yet alone pronounce. This ‘spider’ was discovered by fossil collector John Flowers Bentley who was one of the founders of the precursor to Peterborough Museum. This specific fossil is only found in the seams of Collyweston stone.  

Nigel kits me out with boots, hat and an orange hi-vis fleece (you can keep that, he says), and we walk toward the mine’s entrance through a gate. So far, it’s almost unremarkable but within a couple of minutes, we’re in and all is still. It would be quiet too, but I'm talking. Lime oozes out of the slate and there's the beginnings of stalactites. It’s an underground cathedral with a stillness I’ve not experienced above ground. A sense of calm surrounds us and I feel no need to fill this space with talking. Nigel asks if I’d like to see the old tunnels and despite being claustrophobic, I do – they are narrow and low, twisting and turning this way and that. The tradition of Collyweston slating dates back more than 600 years and the epicentre of that is right here where I am standing. These tunnels are now obsolete and instead the stone blocks (known as logs) are now mined by a robot who asks less questions than I do. 

Collyweston slaters from times gone by – second from the left at the back is Nigel Smith's great grandfather William. Many of the traditional methods of slating are still used today.

The world today would be unrecognisable to the earliest miners but many of the handcrafted elements of Collyweston slating remain true to tradition. To watch someone work with the slate is to witness a mindful vocation with a rhythm, an unspoken language. In the past, mined stone logs were left outside to split naturally into slates. This required several winters’ worth of frost but this method died out in the 1960s and the mine closed.  

In 2016, Claude N Smith Ltd re-opened the slate mine – slate source miners needed to remove more than 100m of rock to form an access tunnel. This coincided with a study using modern freezer technology by Sheffield Hallam University and Historic England who were researching a method of splitting the slates that wasn’t reliant on unpredictable weather. Today, Nigel uses a series of refrigerated steel containers to mimic the natural process making it all the more efficient. 

Inside the mine which re-opened in 2016.

Once split, slates are taken inside to the workshop and that’s where I meet Nigel’s team. Carl clives (breaks) the stone with a dressing hammer and then chips and dresses each individual slate using authentic hand tools. It then passes through other hands, each with a specific role until it becomes the final product.  When I visit, there are crates of slate bound for Cambridge University. Keen to see the next part of the process, I’m delighted when Nigel invites me to go with him to Cambridge University to Christ’s College where his team are busy re-slating the roof of an accommodation building. 

On the way, I quiz him about the slate and pause for only a few minutes to type out an email on my phone. This silence is noted by Nigel who laughs “that’s the only time you’ve been quiet this whole journey.” When we arrive, he explains the Collyweston connection. Henry VII’s mother, Lady Margaret Beaufort, who re-founded Godshouse as Christ’s College in 1505, lived in Collyweston and was one of the richest women in Medieval times. In 2018, the remains of her former palace, where she once lived in the village, were discovered. The project was led by members of Collyweston Historical and Preservation Society (CHAPS). In the coming years, with help from the University of York, the society will carry out further excavations. Much of this is only possible thanks to the understanding of villagers, some of whom allowed the group to dig in gardens in pursuit of this historical gem. Visit the Northamptonshire village and you’ll find it hard to believe it was the centre of power in Lady Margaret’s era.  

Viv Smith outside Christ's College, Cambridge underneath a statue of Lady Margaret.

A statue of Lady Margaret presides over the main gateway to the college on a plinth resplendent with gold highlights. It’s an extremely ornate frontage and a reminder that you’re entering a place of greatness. Charles Darwin being just one of the many noteworthy alumni.  Phase one of re-slating the roof of Christ’s College was completed in 2021 and now the team have moved onto Phase Two. Clare College, another of Cambridge University’s colleges, will be the next project.  Up on the scaffold, I’m able to look down over the roof at those sections already complete. In total, the completed roof will have taken 700 square metres worth of slate. These measurements are all calculated by hand by Nigel and minimise waste. 


On the roof of Christ's College, Cambridge.

In my head, I have a plan – I will ask if I can have a go. After all, the best way to learn is to get stuck in. All seems calm up here, it’s nearing lunch time and the streets below are packed with tourists. It’s a balm for the soul to be away from it all. I meet Shaun Cummings who has been a Collyweston slater for more than 20 years. I watch his careful work for a while before seizing the opportunity to ask if he will show me how to fix the slate – they are never referred to as tiles. Shaun, clearly proud of his work, looks as if he may give up the trowel but I know that if it’s not perfect, it will be taken down as soon as he hears me descend the scaffold. Passing me a slate, he helps me apply a little lime mortar to adhere the slate to the roof. It’s not elegant but I am enthusiastic. 

Clare with Collyweston slater, Shaun Cummings.

Collyweston slates are random sized and shouldered – in short, the slates’ top corners are angled and fixing each to the roof is an art. Each individual slate has to be laid in relation to the two slates below to give adequate side lap. This lap over the shoulders prevents any leaks, something that’s especially important. Slates are secured to a batten with a nail through a pre-drilled hole. I place one slate and am handed another. It takes me long enough to do these and it’s obvious which ones I have had a hand in. Nigel hands me a pencil and tells me to write my initials on so I’ll be able to see if they are still there next time I visit. I look at Shaun and hope there will not be arguments about this later. Over time the slates will become a honey colour through the process of oxygenation and some freshly mined slates indicate various stages of this  – steel grey where minimal oxygenation has taken place to tones of butterscotch where a crack has allowed the air to get in. Before reopening the mine, work such as this would have been practically impossible with only reclaimed Collyweston slate to work with. This lack of material led to a delay in roof repairs where only this slate was permitted on heritage grounds. There are many properties with Collyweston roofs, some more notable than others but the largest singular Collyweston roof is the Guildhall in London. This was re-slated in 10 phases in the 1990s by Nigel’s dad, Claude. But the reach of the material extends far beyond our shores with one impressive example in the US. 

Old Westbury Gardens, Long Island, New York.

Old Westbury Gardens in Long Island, New York, has featured in many films including North by Northwest in 1959 and was once the private home of famed American businessman and lawyer John Phipps. When John married Englishwoman Margarita Grace whose family owned what was to become Grace Steamship Company, he wanted to bring a little of her home country to their home. The year was 1903 and the only way to make this happen was to bring the English over in the form of George Crawley – an enthusiastic design student whom John’s sister met during a trip to England.  Two years later, a group of slaters including Arthur Osborne, the great great grandfather of Collyweston slater Tom Measures who works for Claude N Smith, sailed across the pond to begin work on the 500 square metre roof. In 2020, Tom and three of the team headed there again to re-slate the roof his grandfather had originally worked on. These connections give new meaning to a craft that is hundreds of years old.  Collyweston might only be a small village but it’s certainly made its mark on the world. And underneath a beautiful Collyweston slate roof in Cambridge, there are students who will make their mark on the world, too.