Unshaven after a day of call-centre holiday work, he sips his way slowly through a frappuccino.

It’s only when Kieran pushes back his hair that you notice a long, fading scar on the upper left side of his forehead.

Kieran, 22, has just finished his first year of medical studies at Glasgow University.

Three years ago he was celebrating having achieved the same feat at St Andrews Uni.

The time in between has been spent undergoing intensive speech therapy and rehabilitation.

It was summer 2009 when Kieran celebrated a friend’s birthday with a raucous night out in Glasgow.

A journey back to his girlfriend’s place, in St Mungo Avenue, Townhead, began with Kieran waving his mates off and ended in blackness.

He never made it back to Nadia’s.

Instead, he woke up the next morning at home in Prestwick, bleeding profusely, with a large hole in the front of his head.

His parents rushed him to Ayr Hospital, from where he was transferred to Glasgow’s Southern General Hospital.

He was kept in for two nights and after a CT scan was allowed home with his parents and given a leaflet on how to deal with concussion.

But it did not take long for things to start going wrong.

“I knew I was getting slower, my brain felt slow and my speech had started to go,” explained Kieran.

“But although I was struggling, when the time came for me to go back to St Andrews to start second year, I was adamant I was going.

“Not that I remember, but my parents and my girlfriend have since told me.

“When I got to St Andrews – that is when I start to remember bits and pieces.

“Everything started to collapse – I developed something called a neurological stammer and stuttered on every word.

“People who stutter tend to do it on every sixth word – I stuttered on every single word.

“My personality had changed, my moods had changed, I was severely depressed, I couldn’t concentrate and my memory was badly affected.

“I couldn’t walk down the street by myself. I couldn’t be in cars without panicking. I was afraid constantly – and of everything.

“I was classed as having severe depression with anxiety and post-traumatic stress disorder.”

A leave of absence from his university studies was arranged.

After suffering a breakdown at St Andrews, his GP referred him to the Douglas Grant Centre, a specialist head injury unit, in Ayrshire.

It was here that he was diagnosed with post-traumatic stress syndrome, and his original medical notes reviewed.

He was diagnosed as having severe bruising to the frontal lobe of his brain.

But, to this day, Kieran has no memory of what happened that night – nor of the months that followed.

Examinations by medics and police all reached the same conclusion; the head injury was inflicted by a downward blow from a blunt instrument.

The belief is Kieran was attacked.

There was no CCTV, no witnesses to the incident and Kieran had been drinking heavily.

But aside from the many physical demands of his injury that needed to be addressed, Kieran also had to deal with the psychological implications.

Given that academic success had come so readily to him at school, to wake up unable to simply communicate was a nightmare.

His ambition to make a career in medicine was in tatters.

“My brain just didn’t work any more,” he said.

“I used to be able to memorise things almost immediately, but that had all gone.

“My personality had changed too. I wasn’t the same person anymore, and I knew it. I didn’t recognise myself.

“Your voice is how you project to the outside world. I put so much into getting my speech back, I worked at it constantly and then when I got it back it was a complete anti-climax.

“I still felt terrible because it was my brain that wasn’t working.

“I was so much slower than before. My brain used to flow when I was thinking, but it just wasn’t working.”

And although Kieran knows there is someone out there who could tell him what happened that night – his assailant – he doesn’t dwell on it.

In the immediate aftermath of the attack, the 22-year-old said his anger was all-consuming, and not just for whoever bears responsibility for his injuries.

“When it comes to whoever did it, it didn’t matter,” he said.

“I hated everyone. I hated myself. I hated having to go to speech therapy.

“I hated what was happening to me. And yet, I would go to rehab and I wasn’t even close to being the worst there.

“Every week, in this city, boys will suffer terrible head injuries and won’t wake up, or will be in a wheelchair for the rest of their lives.

“I didn’t care – I hated them as well. I wanted me better and it made me a horrible, selfish person to be around.

“I hated my Dad, because he was on my back all the time – to go to speech therapy, to work at it, to not indulge myself by sitting about – ultimately, though, it was him who made me get better.

“My Mum was there emotionally – she was a rock that way, whereas my Dad was always pushing me.

“If it wasn’t for the fact that I had great parental support and emotional support from my girlfriend, I would have committed suicide. I am sure of it. ”

Kieran credits that support, as well as a dollop of “luck”, to the reason why he is where he is now – back at uni with his vision firmly trained on a career in medicine.

Now there is no bitterness as he recounts the last few years.

“I am a different person now,” he said.

“My brain works differently. My personality is different. I am 22 – I feel like I am 42. It’s strange – you see how fragile everyone is, but also how strong you can be.

“Because my injury was to my frontal lobe, I still have problems with things like impulse control.

“I have mood swings and, if I’m tired or stressed, I’ll explode and say whatever is in my head, terrible things.

“But if and when I pass medicine I’ll be a better doctor. I might not be as book-smart as other doctors but I’ll know what it’s like to be a patient.

“I’ll know what the psychological aspects of such an injury are and I’ll know what families go through.

“I’ve just passed my first year, with a B2, which is very good – better than I got at St Andrews.

“That is just because I have had to work so hard. I used to be able to rely on my brain.

“I could sit in lectures and not concentrate too much and it would still go in. Now I work so hard because I have to .”

There is still some way for Kieran to go before he puts on a medic’s white coat and picks up a stethoscope.

But the fact he has it in his sights is something he admits few would have predicted.

“It might not sound it, but I am so lucky,” he said.

“The kind of injury that I have had, to then be in a position to go back a few years later and resume studying medicine, just doesn’t happen. Without the support I have had, it wouldn’t have.”

Light at the end of the tunnel, perhaps, but it has been a long and, at times, lonely road for Kieran.