Given that he's only 11, that's saying something. "I like using older ideas," says Chalk, who attends the Lothian Specialist Music Unit at Flora Stevenson Primary School in Edinburgh. He has no pretensions about his source of inspiration. "I got very interested in the Jacobites when we did a project on it in school."
The idea of the two brothers being consigned to opposing armies as a ploy by their father, Lord Ullapool, to ensure that at least one survived, came to him out of the blue.
It was only later, through schoolwork, that he heard of a real life instance of such a case during the Battle of Culloden. In Matty's play, the calculating father's plan misfires. The sons wind up killing each other, shouting "brother" as they plunge their weapons into each other.
The play is being shown as part of this year's Royal Court Young Writers' Festival, Storming. It is one of six plays, four of them under 15 minutes and two of them longer, being professionally directed and performed. They represent the pick of a crop of more than 200 entries sent in by young people from all over Britain and reflect a wide range of styles and interests.
The other Scottish play in the Festival is Business as Usual by 12-year-old Michael Shaw, who describes it as "about a surrealist business run by an amazingly weird consortium of characters". Flat U Lent, an accommodation agency, is run by an orangutan, an alien and an accountant with sticky fingers. It's as madcap and zany as Matty's play is dark and brooding.
Other plays include Backpay by Tamantha Hammerschlag, about the prevailing unease within and between cultures in the new South Africa and Drinking, Smoking and Toking by Stuart Swarbrick, about the dilemmas presented by peer pressure.
Along with the productions, a new audio play, Lifelines, is being presented every evening at 6pm from tonight and readings of other plays developed in the Festival will be performed, as will three international plays generated by the Royal Court International Programme.
In addition, "net.play" is being created by five writers throughout the world and will be read at the Royal Court. It involves young writers in India, South Africa, America and London collaborating on a new play via the Internet, guided by a director from the Royal Court, over a period of three weeks. The edited version will be published on the Internet without copyright for people to use as they wish.
Storming runs from October 28 to November 16 at the Royal Court Theatre Upstairs at the Ambassador's Theatre. For a full festival programme and bookings, ring 0171 565 5000.