HOW much do you know about Hadrian's Wall? Chances are those who tune in to Robson Green: Walking Coast to Coast will come away having learned a few gems. The presenter is charting its history by following the 84-mile path for a new three-part series on Channel 5.

Hadrian's Wall has stood for almost 2,000 years, built by the Roman army on the orders of the emperor Hadrian following his visit to Britain in AD 122. It remained as the north-west frontier of the Roman Empire for close to three centuries (with the exception of the short period when the Antonine Wall was manned).

The Grantchester star describes it as "one of the greatest feats in construction history", up there with the Pyramids and the Panama Canal. Today, Hadrian's Wall is lasting testament to the skill and ambition of the Roman Empire.

It's a Thursday morning in early January as Green's voice drifts down the line from Northumberland. Once we have finished chatting, he and his partner Zoila Short plan to take their daily exercise with a walk along the nearest section of the wall, only minutes from their home.

The pull of the wall is something that Green has felt throughout his life. He first visited as a seven-year-old and while it was some years before he saw it again, Green credits that afternoon with stoking a love for history that he never felt during lessons at school.

Later, before becoming an actor and presenter, he worked as a draughtsman at Swan Hunter in Wallsend during the 1980s. Green recalls how his interest was piqued by the excavation of Segedunum Roman Fort, only a stone's throw from the shipyard.

HeraldScotland: Robson Green: Walking Coast to Coast. Picture: Channel 5Robson Green: Walking Coast to Coast. Picture: Channel 5

Green has previously walked various sections of Hadrian's Wall, but never the full length. That changed last summer when he was asked to present Walking Coast to Coast, covering a journey from Wallsend on the east coast of England to Bowness-on-Solway in the west.

His passion for its stories is palpable. Here, Green shares some of his favourite moments traversing Hadrian's Wall and the fascinating nuggets gleaned along the way.

Surprising revelations

"I didn't know Segedunum at Wallsend was inhabited by more than 600 Iraqi soldiers," says Green. "I didn't know Housesteads had soldiers from Algeria and Romania. I didn't know Vindolanda had soldiers from Syria. There was a melting pot of cultures on the wall.

"The biggest revelation was when I met forensic anthropologist Dr Trudi Buck. Some people enjoy finding coins, pottery or clothing – Trudi loves bones.

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"Technology has advanced to the point where, from a skull, you can not only tell the age and gender, but you can also tell hair colour, ethnicity and eye colour. From a skull, a neck, a chest, Trudi can tell you where that person is from and she can paint a lifelike picture.

"She found the remains of a 12-year-old girl from Syria. I thought this was amazing because it wasn't speculation that people from all over the world lived here. I realised it was a melting pot. And that the Romans never left.

"The generations have gone on and on. And they are still here. The DNA is still here."

The psychology of Hadrian's Wall

"Hadrian was a man obsessed with power and symbolism," says Green. "He loved monuments named after him. It is basically saying: 'I have strength, I have wealth, I have power – so come and have a go if you think you're hard enough.' That is what the wall represented.

"The psychological impact of being told, whether it is disinformation or not, that there were terrible people to the north of this wall called barbarians – if we don't look after this wall, they are going to get over it.

HeraldScotland: Hadrian's Wall. Picture: GettyHadrian's Wall. Picture: Getty

"The wall was this living, breathing entity that I'm sure had a profound psychological effect on the people who worked and lived alongside it."

A remarkable feat of ingenuity

"Millions of tonnes of stone were brought up along the Cheviot Hills to create a border east to west that is 10ft wide and, in some parts, over 32ft high and more than 80 miles in length," says Green. "The sheer scale of it is mind-boggling.

"When you deconstruct how they did it: 'Where did they get the stone from? They got it from Gelt Woods [in Cumbria]. 'How did get the stone from there to here?' It was manpower. It was built by soldiers. Not only were they a formidable fighting force, but they were skilled craftsman.

"They were stonemasons, engineers, architects and blacksmiths. It took them six years to build and it was exact. It was no coincidence that the wall runs parallel to the River Tyne because all the stones had to be bound together by mortar [which needed water]. That is clever and inspiring and life-affirming.

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"It must have been a sight to see 15,000 soldiers constructing this thing. The wall at one time was whitewashed. That must have been extraordinary to see from miles away."

A close encounter with wildlife

"We did a pre-production recce," says Green. "The wall is on my doorstep, so I was able to sort out locations and permissions, such as parking, where to eat, what's the best way of getting the cameras up the hill and so on.

"On one walk, I said to Zoila: 'Would you look at that? It's a bloody snake!' It appeared to be dead and I was thinking it must have escaped from a zoo. I decided to give it a prod and take a selfie – being the narcissist I am – and it went for me.

"It was well and truly alive and just missed my neck. We both screamed. I realised a split second after it went for my neck what a coward I was. I took off like Usain Bolt. Zoila is a bit younger than me. She is fast and fit, but I passed her like a gazelle. The snake was a European viper.

"In Northumberland, there are millions of rabbits. I didn't know it was the Romans who brought rabbits to this country. Alongside carrots and plums and sanitation and roads and education and a coin economy, who would have thought rabbits?

HeraldScotland: Sycamore Gap at Hadrian's Wall. Picture: Kate Buckingham/NewsquestSycamore Gap at Hadrian's Wall. Picture: Kate Buckingham/Newsquest

"There have been bones from zebras and ostriches found. It was an empire. People from the Middle East and Africa came here. They brought their belongings and livestock. A lot of exotic animals were roaming the hills of Northumberland 2,000 years ago."

His favourite section of the wall

"Sycamore Gap. It is a beautiful section. It is near what you call the heart of Hadrian's Wall. There are peaks and troughs in the wall and positioned dead centre in one of the troughs resides this extraordinary sycamore tree.

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"To the north is the Northumberland National Park and The Pennine Way, and to the south is the Tyne Valley. On a good day, sitting next to Sycamore Gap having a coffee or a picnic, on your own, watching the sunset in the west is astonishing."

Robson Green: Walking Coast to Coast continues on Channel 5, Thursday, 9pm