Dahl's stories are still as popular as ever.  Today's adults, who grew up with them, remember them with huge affection.  And today's children enjoy their combination of fantasy and reality just as much.  He creates colourful characters - think of the insects in JAMES AND THE GIANT PEACH, and wonderfully nasty baddies - think of the Giants in THE BFG or the Grand High Witch in THE WITCHES. 

Like many classic stories, the fantasy often stems from reality.  In THE BFG, Sophie is an unloved child living in an orphanage.  Her very real situation is transformed when she is snatched through the window by the Big Friendly Giant.  She, like many other Dahl child characters, ends up, against all the odds, triumphing against injustice. 

The Boy in THE WITCHES helps save all the children of the world.  Sophie's passionate action stops the children of England being eaten by Giants.  These are huge matters of life and death.  And by using a child protagonist, Dahl empowers children to believe in themselves and to question unfairness and cruelty. 

So young readers identify with the young heroes and heroines, and revel in the often anarchic representations of eccentric and unpleasant grown-ups.  Dahl is also remarkably adept at taking traditional ingredients of fairy tales and recycling them to give his work a contemporary, yet timeless, feel.  For example, many fairy tales use kings and queens.  Dahl's Queen in THE BFG happens to be the Queen of England.  He never actually refers to her as Queen Elizabeth II, but the reader immediately imagines our present Queen, particularly when Buckingham Palace becomes a location for the story. 

And, just as giants and witches abound in traditional stories, Dahl brings them right up to date.  His Giants threaten today's children, as do his witches in THE WITCHES.  Not for him the pointed hat and broomstick.  His witches are altogether more dangerous, because they can easily be mistaken for ordinary women.

Dahl's stories are always on the side of fairness and justice, but he never overtly preaches or underlines a moral.  He is not afraid to bring out the darker aspects of a story and he cleverly couples this with wonderful humour.  He always said that one of his main aims was to make children laugh.

I approached THE BFG with trepidation.  The book had rapidly become a children's classic.  It is a splendid mix of the scary and the subversively funny, involving children-eating giants, whizzpoppers - perhaps the first time that breaking wind had appeared in a children's book - child abduction and the introduction of the Queen of England as a character. 

Fantasy ideas like blowing happy dreams into children's bedrooms jostle with a contemporary world of helicopters on a mission to catch the giants.  Particularly effective is the growing warmth of the main through-relationship, a kind of non-sexual love story between Sophie, a feisty orphan, and the Big Friendly Giant. 

These two social misfits struggle against evil and eventually save the world's children.  The story had all the makings of an exciting and inspiring play, but there were glaring problems about staging it.  The main problem was one of scale. 

Would the audience expect to see a little girl and a twenty-two feet high giant?  Puppetry was a possibility, but it felt wrong to have an actress play Sophie alongside a huge puppet BFG, or to have an actor play the BFG alongside a small puppet Sophie. 

Eventually, the solution came when I realised that the book is divided into two halves.  The first half concerns one human being (Sophie) in a world of giants.  The second half involves one giant (the BFG) in a world of human beings. 

So, in the first half I used a puppet Sophie (operated by the actress Sophie) with human beings playing giants.  In the second half I used a huge puppet BFG (operated by the actor BFG) with human beings playing human beings. 

This seems to have worked well.  I also introduced a play-within-a-play device, which meant that the story could be acted out by a group of children at a birthday party.  It is true that the notion of 'let's do the play right here' risked coming over as a cliché, but the possibilities for inventiveness and apparent improvisation seemed to me to be ample compensation.  Hopefully it works!

Much of my book THEATRE FOR CHILDREN: GUIDE TO WRITING, ADAPTING, DIRECTING AND ACTING (Faber) is devoted to the belief that the demands of children's theatre are considerably different from those of adult theatre. 

Children don't automatically have theatre manners.  If a play doesn't interest them, or bores them, they won't sit politely and clap at the end as adults do.  They will shuffle in their seats, talk to their friends and, even if they don't really want to, insist on being taken to the loo! 

Our job is to accept this challenge, and produce work that rivets children to their seats, interests and inspires them, and makes them unable to take their eyes and ears away from what is happening on stage.  Quite apart from a strong story, we have to find ways of telling the story that emotionally involve and trigger the imaginations of our audience. 

This means that action is as important as dialogue.  It is unlikely that children would sit quietly through a play consisting of two characters sitting down having a conversation.  They need to be doing something as well as talking about it.  It is also, for me, important to employ as much theatricality as possible in the production. 

The 'magic' of theatre still works on the most sophisticated children.  Lighting, sound effects, scenery, costume, illusion, puppetry, mime and music all have a part to play. 

When I write a play for children I am looking for what I call 'suddenlies'.  These are the theatrical equivalent of sudden page-turning moments in a book, things to stimulate, things to encourage the audience's attention not to wander.  On each page I try to craft several suddenlies. 

These may be a sudden lighting change, a sound effect like thunder, a new character coming in, a musical sting, an unexpected twist of plot, a sudden new thought etc. etc.  For me there is nothing more exciting than being in a theatre watching a house full of children reacting positively to my work.  It really is a big challenge, and it never gets any easier.  But when it works, it creates an infectious buzz.

 Very difficult to answer this - I have been fortunate enough to adapt several wonderful stories, including six Dahl titles, Philippa Pearce's wonderful, haunting TOM'S MIDNIGHT GARDEN, and, for younger children, Judith Kerr's classic picture book, THE TIGER WHO CAME TO TEA. 

I suppose what grabs me is a certain magical quality that grips the imagination.  Tom is able to go back in time to meet a Victorian girl called Hatty.  Young Sophie and her mother take it in their stride when the doorbell rings and a  tiger asks to come to tea. 

Both stories, on the surface, are implausibly impossible.  But their authors brilliantly make us believe not only that the story could happen, but that it really did happen.