The Duke and Duchess of Cambridge took turns behind the wheel of a hi-tech tractor during a visit to a farm that aims to become carbon neutral.

William and Kate had a tour of Manor Farm at Little Stainton near Darlington, which has been run by the same family for 145 years, and which uses 21st-century technology to achieve sustainable farming.

William likened the GPS-controlled tractor to the helicopters he flew when he was an air ambulance and RAF search and rescue pilot.

Farmer Stewart Chapman, 51, who sat in the tractor on both journeys with the masked royals, said afterwards: “They both wanted a go and didn’t need any persuasion.

“Once they got used it, it was fine.”

The automated tractor had a route across the field pre-plotted using GPS and is designed to use less fuel by efficiently covering the ground, cutting emissions.

Two weeks of royal mourning for the Duke of Edinburgh ended on Friday for the Windsors, and William and Kate were out of their black mourning outfits and dressed casually for the countryside.

Kate was in a Fair Isle style jumper, wax jacket, boots and skinny jeans, while William was in a padded coat, navy blue chinos, and sturdy boots.

The Cambridges also joined the farmers’ daughters Clover, nine, Penelope, seven and Wren, four, and their lambs named Dumbledore and Heather.

Clover said afterwards: “It was very exciting, but it was also quite nerve-wracking.

“She (Kate) asked me about when my friends came over were they surprised at how well I train the lambs.”

Mr Chapman and his wife Clare Wise also showed off their calving cameras, which send them a text message when one of their cows is about to give birth.

William joked: “Everyone has a social media problem and here you are, with cameras and text messages about the cows.”

The farm, which has been in the family for five generations, also keeps its grass long enough for nesting birds, and a nutritionist lays out how much food the livestock should be eating.

In a cow shed, William and Kate grabbed a handful of the silage and ran it through their fingers.

Ms Wise, 40, said afterwards: “They asked how do we know what good feed looks like and the duke was very knowledgeable on feeding livestock and said how this year has been a nice sample and handles particularly well.”

William has previously told of his passion for farming, revealing that his children are already playing on tractors.

He will inherit the Duchy of Cornwall, which covers more than 130,000 acres across 23 counties, when his father becomes king.

The couple also chatted with seven North Yorkshire and County Durham farmers about the challenges caused by the pandemic and isolation.

William said: “Home schooling must be difficult. Home schooling and farming is another level.”

He added: “The pandemic takes away your coping mechanisms. We all have ways getting through the days when you strip that away and at home all the time it starts to wear on people.”

Ms Wood said after the visit: “It’s been lovely as they are role models for our three children.

“They are very knowledgeable about farming and had a beneficial discussion on both sides.”

Remarkably, the family kept the royal visit secret from their children until breakfast time.

Adam Bedford, NFU regional director, said: “They were both knowledgeable about sustainable farming and had a lot of good ideas on how farmers can adapt.”

Kate and William will mark their 10th wedding anniversary on Thursday.