Chris Terryl is a journalist, the only person that, being 55 years old, was able to go through the full training and to qualify as British Commando (Green Berrets) and later on to follow the troops in Afghanistan.
The story was tolsd in a book (Chris Terryl - Commando) as well as in an ITV 2007 TV series, eventually produced in a two DVD pack.
It is also not difficult to find with torrent.
http://www.itv.com/News/commando/default.html
The book is absolutely great. I hope the movie should be the same.