The moving story of young autism client Sam Mills and his dog Willow touched  the hearts of millions  of viewers when they featured on BBC's Children in Need, broadcast in November.

Seven-year-old Sam recently went on a trip to Alton Towers with his mum, dad, young sister and dog, and had a great time. His favourite ride was a wooden roller coaster called the Wickerman.

Nothing unusual about that, you might think.

Except that little more than a year ago, nothing would induce Sam to leave his house, let alone go somewhere as noisy and busy as a theme park.

Sam, who lives in Sheffield with mum Emma, dad Steve and four-year-old sister Ellie, was diagnosed with autism at the age of five. Bright lights, music, crowds, shops all overloaded his brain and he found it difficult to cope.

So what’s made such a difference?  Step forward black Labrador Willow, who has been working with the youngster and his family for just over and year, and in May Sam and Willow qualified as Support Dogs’ latest autism assistance partnership.

The day out at Alton Towers was further proof of the incredible difference that Willow has made to Sam’s life. “He’s a little boy who struggles to be happy, who is over the moon,” she says, as boy and dog sit companionably in their sitting room, and then chase a ball around the garden.

Sam’s autism takes very particular forms. He has sensory difficulties - which means he struggles with noise and crowds, has severe anxiety and he also suffers from depression. Unlike lots of youngsters with autism, he is verbal, except when he’s very stressed, and, until Willow came into his life, had no sense of danger.

Says Emma: “Willow can be very calm when she needs to be, but also excitable and daft, gets him playing and distracts him – they are a perfect match. When Sam has a bad day he goes into the garden and plays with Willow and 20 minutes later he is smiling again; she makes him laugh.”

Sam’s problems began when he was three and started to struggle at school; lashing out at people in frustration, and covering his ears in class. He spent increasing amounts of time at the school’s ‘nurture unit, specialist provision for children who struggle in mainstream school.

Over time, his parents could barely get him to school – they couldn’t hold his hand because he hated to be touched and he would run off into the road. Keeping him safe became more and more of an issue and Emma and Steve ended up taking him to school in a disability buggy.   The number of ‘meltdowns’ he experienced increased. Emma had to give up her job working in data management with South Yorkshire Police. “We got to the point where we could not leave the house. We were knocking on so many doors, trying so many things, but nothing was happening,” says Emma.

They applied to Support Dogs for an autism assistance dog and were invited to an open day. “I had a gut feeling that a dog might help him, but I never realised it would be as good as it is,” reports Emma, who did the initial training with Willow before her son and the dog were introduced. A camera crew from CBBC were on hand to record their first ever meeting and it’s a touching scene as Sam, initially wary, starts playing ball with Willow, and his face breaks into a lovely smile. His parents watch, tears in their eyes.

And when the CBBC crew came to film three months after their initial visit, he chatted to the presenter who could see an enormous change in him.

Straight away Willow and Sam had a really close bond.  Sam struggles with his emotions but is now less anxious because Willow has such a calming effect, acting as his safety net and keeping him calm when they go out. Sam is attached to Willow by a wrist strap, as he doesn’t like a harness. Crowded streets and busy places are not a threat anymore and Sam is no longer a danger to himself by running into the road.

“Sam wants to go out now!” says Emma.  “He will actually ask to go to the shops or to the woods. She has given him confidence and makes him feel safe. When he struggles – and he still struggles – Willow is there. Sam will lie down on the floor because he can’t run off, and Willow will lie down with him. It makes such a difference and we know that Sam is safe.

Although the main reason for getting Willow was to get Sam out of the house in safety, she has also done wonders for his self-esteem and confidence, and Sam will now chat to members of the public when they come up and ask him about her.

As Sam’s main carer who bore the brunt of his moods, and on whom Sam was utterly dependent, Emma now reports that Sam has now transferred much of that dependence to Willow, meaning she and her husband can go out together occasionally.

The family are also trying out new things – they went to a café for Sam’s granddad’s birthday breakfast, which would have been unthinkable a year ago. Getting Sam to bed now takes 20 minutes as he is so much calmer – it used to take two to three hours. Sam is now at a special school in Sheffield and once he settles in Emma hopes to be able to go back to work. They are moving towards a normal life, courtesy of their wonder-dog Willow.

“I don’t know what we’d be like if we didn’t have Willow. Since we’ve had her we’ve had a massive lifestyle change,” says Emma. “The doctors wanted to put Sam on medication for his anxiety, but Willow has reduced his anxiety to such an extent that we can work on it with him without drugs. They had never come across an autism assistance dog and they could so the difference in him.

If you had seen him last year you would have seen a very different child. Thank you Support Dogs.”