'I joined a pothole repair crew and it's tougher than I thought!'

With an estimated one million UK potholes, the Daily Express decided to fill one in - and found there's more science involved than we realised. We have all suffered that grimacing judder when driving over a pothole, later having to check for any expensive damage to our tyres.

So I visited the research and development base of Holcim UK - one of Britain's largest aggregate and asphalt suppliers - in Ashbourne, in Derbyshire, to study the science behind potholes and have a crack at fixing one. And the choice of the county is apt - as RAC data claims Derbyshire has the worst potholes in the UK, with 38 per cent of its minor roads in their critical 'red' condition and 28 per cent of their major roads in the 'red' danger category too.

First of all I can confirm you will never have to drive over a pothole I fixed, as the Holcim crew kindly dug out strips of their staff car park on site for me to hone my road repair skills.

Secondly we need to understand what actually causes the crumbling road hazards - and there is no-one better than Holcim UK's technical director Phil Sabin to explain it.

As I stared into the perfectly square hole where an unlucky employee's parking spot used to be - donned in the firm's safety attire of hard hat, goggles, gloves and fluorescent yellow trousers and jacket, Phil told me: "Obviously a real pothole is not this neat!

"A pothole's primarily caused by water infiltration. Moisture seeps into cracks and beneath the asphalt layer, when it gets cold trapped water freezes and expands, exerting pressure on the asphalt and weakening bonds.

"Over time, vehicles passing over exacerbate the micro-cracking. Then as temperatures rise and ice melts, air pockets that compromise the integrity are left behind and under repeated stress the unsupported asphalt eventually gives way - and that's your pothole."

So the creators of potholes are water, pressure and extremes of temperature. How do we fill one in so the road doesn't fail again?

What is eye-opening to learn, as I look around their research labs, is how asphalt is not a 'one size fits all' product.

It's a composite of aggregates, usually crushed stone like granite or limestone, and bitumen which comes from crude oil and binds and waterproofs it all.

But depending on what the road is being used for, depends on what sort of mix.

They make asphalt for our driveways, for bus lanes - so able to withstand that huge weight - and cycle lanes which may need a stone mix that gives a good grip in the rain.

They even have reduced carbon options being explored all the time with crushed up old solar panels or wind turbine blades to reduce the amount of bitumen.

And it's not always boiling hot asphalt either - for my attempt at a pothole 'repair' I used a new cold-mix product which reduces carbon by not needing to be heated before pouring.

The Holcim crew kindly kicked off the repair for me by applying what's called a tack coat, a water/bitumen emulsion - into the hole and inside walls using a watering can.

That ensures the base of the pothole bonds with the bottom layer of new asphalt and reduces the chance of air pockets.

Then I'm handed a big bag of cold-mix asphalt and pour it in, making sure to break up any lumps with the tip of my shovel - it feels like I'm doing a spot of gardening.

Out came the rake as I had to smooth it over and use the back of the rake to scrape any loose asphalt off the road - or in our case car park - and back into the pothole.

The next task felt very satisfying as I was handed my tamper - a long metal rod with a small heavy square flat end for thumping down on the asphalt and compacting it nice and neat.

We did two layers of asphalt and Phil was making sure I was getting it right into the corners and sides. He stressed: "If the repair fails that is where it will happen - not in the middle but at the edges."

Then it was time for the kid in me to have some fun, as they fired up the engine on the MBR pedestrian roller - so called as you push it like a giant, powered lawnmower.

"This is brilliant!" I yelled over the machine's din. The rest of the crew just looked at each other. They've been there and done that.

After rolling the newly filled pothole a few times we switched on the machine's vibrating mechanism and shook the new asphalt patch job to flatten out any little air pockets and get it extra compacted - then the job was done.

Phil kindly called me a "natural" but his patient team of tutors were just looking at my handiwork - and pitying the unlucky colleague using that parking bay next week.