• Video report by ITV News Correspondent Damon Green

For 11-year-old Jack Johnson, this Saturday will see one of his best friends play a crucial role in the Rugby World Cup final.

The schoolboy suffers from Duchenne muscular dystrophy and his mate is none other than Owen Farrell.

Diagnosed age four, Jack is one of just 2,500 boys in the UK to have the genetic condition which causes progressive muscle degeneration and weakness.

When the England captain scores - which is fairly often - he can be seen locking his fingers together in a show of support for Joining Jack, a charity set up by Jack's parents to aid research into the condition.

Every year it raises thousands of pounds, with the support of England's star player meaning the world to them.

Not only does the sign raise awareness of the charity, Jack is hoping it will also signify lots of points for England against South Africa.

"It would make me feel really happy and warm inside because I know he's here to join other boys and me," he said from his Lancashire home as he looked forward to Saturday's match.

Jack's mother Alex, is full of praise for the rugby star: "It's testament to him and the incredible person that he is that he remembers to do it, he really does want to help Jack and all these other boys living with the condition."

Jack's mother has prayed the England player. Credit: ITV News

One day Jack hopes to join in with his favourite sport - but first a cure needs to be found.

For now, watching his hero is enough.

The Rugby World Cup final is on ITV on Saturday from 7am. You can watch it on the ITV Hub.