For a young boy suffering from a genetic neurological disorder, to be a mascot at an international football match was a huge honour – but also a very scary prospect.

Max had trained for the big day for several weeks – watching video clips, being motivated by his family – but was still very nervous when his moment came.

But Swedish international midfielder Kim Kallstrom was on hand to hug the eight-year-old and put him at his ease – enabling the young football fan to complete his duties without incident.

Now a letter from Max’s father to Kallstrom, thanking the player for his attentions, has gone viral on social media.

Max was one of eleven children suffering from Williams syndrome who were chosen to be mascots for the World Cup qualifier between Germany and Sweden in Gothenburg.

The disease gives children a cheerful demeanour but leaves them with physical and mental disabilities, and problems with concentrating and relating to the outside world.

"I am writing to you because I'm not quite sure if you understand how much of a difference you've made to us,” said Max’s father Emil in the letter to Kallstrom.

“Tuesday saw my son Max do something very special. For other children, it's really about 15 minutes of concentration and nervousness as well as an incredible joy of having been able to meet the national team.

"Because of your actions, Kim, my son was able to experience exactly the same feelings as everyone else: pride, a sense of being special, ‘I did it’ and the joy."

The letter has been shared over 15,000 times on Facebook and attracted almost 90,000 ‘likes’.

But Kallstrom denies doing anything heroic.

He said: “Despite Max being a little nervous in the players’ tunnel, together we were fortunately able to make it a very positive experience.

"In a situation like this I act more like a neighbour and a parent rather than as the footballer I just happen to be. I realise I have a responsibility to the parents, but also to the children who enter the pitch with us.

“I try to be calm and comforting, and it is usually enjoyed by kids."