AS a child, Ronnie Pinder was never invited to any birthday parties.

It wasn't until he was an adult and father to his own children that he realised that was unusual.

"My girls were getting invited to lots of birthday parties and I said to my wife: 'Why are parties so popular these days - we never used to do that when we were kids'. My wife said: 'What do you mean, of course we did!'

"It was only then I realised other people were getting invited to parties but I wasn't. Don't feel sorry for me, I was oblivious to it all."

The 46-year-old father of five was diagnosed as being on the lower end of the autistic spectrum 18 months ago. He was found to have Asperger Syndrome, a type of autism that mainly affects the areas of social communication, such as reading facial expressions, understanding jokes and picking up social cues as well as problems with imagining alternative outcomes to a situation.

The first clue came after Ronnie filled out a fun questionnaire on Facebook - and the results suggested he could be autistic.

According to the National Autistic Society there are around 700,000 people in the UK living with autism – that's more than 1 in 100. Autistic people see, hear and feel the world in a different way. It is not an illness and cannot be 'cured'.

As Ronnie discovered, autism is a spectrum condition, meaning some people have more severe difficulties than others. Some have learning difficulties and delayed speech. Autistic people may suffer sensory problems and be sensitive to sounds, touch, tastes, smells, light, colours, temperatures or pain.

This is true for Ronnie, who besides his problems with social interaction, suffers sensitivity to certain lights and noise. Before his diagnosis, he was treated for dizziness, vertigo, sensitivity to lights and noise and panic attacks - without doctors being able to find a root cause. All are classic symptoms of autism.

Ronnie isn't bitter about his late diagnosis. Growing up in the 1970s, only children with the most extreme symptoms were diagnosed with autism.

But looking back, he says, it was clear something was amiss - had anyone been looking.

"I'd grown up assuming and thinking I was the average child. I was shy and a bit eccentric and had some little quirks - in fact, all the signs were there."

Ronnie had the classic autistic trait of "stimming" - using hands or feet as a way to self regulate feelings. "Children might flap their hands when stressed or worried or in unfamiliar surroundings," explains Ronnie, who adds he would wiggle his fingers - a habit that stays with him today.

As a child, he made odd grunting sounds - which was another indicator.

Ronnie says there are many adults on the spectrum who have never been diagnosed. "They are the lost generation."

Some adults with autism are well known, says Ronnie. The actor Dan Ackroyd was diagnosed with Asperger's as an adult, as was Springwatch presenter Chris Packham, who has written about his struggles in a new book, Fingers in the Sparkle Jar (Ebury Press, £20).

It took a year after the Facebook quiz before Ronnie plucked up the courage to go to his GP. He underwent tests at the Tuke Centre, based at the Retreat in York. When the diagnosis was confirmed, he felt relief.

He says: "It has changed my life. It was a massive weight off my shoulders. I have finally forgiven myself for what I perceive as my failings. I stumbled into different jobs and have worked always below what I am capable of doing - that is especially common on the spectrum. Routines are very important. My biggest regret is never going to university and taking it further to post graduate study. I always felt angry doing mundane jobs that were not well paid. But I never knew what I wanted to be, and it was a scary thought going to university. Change is horrific - when I change jobs I'm a gibbering wreck for six months. I work in retail because it is safe."

Recently, he has spoken in public about his autism - during Autism Awareness Week as keynote speaker at Tuke Centre and before a body of GPs in York. He is able to do this, he says, because when he is talking about one of his "specialist subjects" he feels at ease - another autistic trait. Try to make everyday conversation and it's a different matter, he says.

He took to Twitter to connect with other adults with autism and hopes his experience helps others - and shows parents of children with autism a glimpse of what can lie ahead in adulthood.

As his doctors have pointed out, he has a successful life, is happily married, with five children and a job. Only 15 per cent of people with autism have a job, says Ronnie.

However, he does feel different. He offers this analogy: "My brain is wired differently, it has a different operating system to most people, but we get the same results." He adds: "I am comfortable now, but it was like being an alien on a foreign planet or being planted in Japan where the culture and body language are so different."

Finally, Ronnie has accepted who he is. He said: "People ask me if there was a cure, would you take it? I say: 'no'. I wouldn't be me anymore. It's not like an illness, it is part and parcel of who I am. Without it, I would not recognise who I was."

Find out more from The National Autistic Society (autism.org.uk) and the Autism Helpline (telephone 0808 800 4104)

Follow Ronnie on Twitter @vinyljunkieuk