Kenneth Branagh is Uncle Horace:

Uncle Albert's first appearance in the film is described as follows: "What looks like a middle-aged Edwardian schoolmaster is sniffing his way towards the children. Uncle Albert moves with a lolloping stride, almost as if he's too big for his body. He is a constant stream of chatter; from complex mathematical equations to the nesting habits of field mice. He's a bubbling font of disconnected information."

Kenneth Branagh plays Albert with great panache and enjoyment: "Uncle Albert's house plays host to five children - my relations - over the summer where they have lots of adventures and where they have to deal with me and my eccentric lists of house rules including no running in corridors and no interrupting me whilst I am writing my yet-to-be published masterpiece called Difficult sums for children. Albert is very interested in mathematics, which is something of a stretch for me as I don't have a mathematical side to my brain at all."

Kenneth was attached to the project from an early stage: "Very kindly John, David and Nick allowed me to come in to see if there was anything we could do in adapting the book to make this invented character more quirky. He's constantly having a series of internal dialogues - he might be talking to someone but thinking about something else, so that he's always a beat behind the band. But he's full of energy and curiosity, particularly about mathematics, and he uses that as a bit of protection from people, because you see at various points in the film a twinkle in his eye, a little bit of contact, a little bit of teasing with his son Horace, a little bit of sensitivity and sympathy for the children and their concern for their father who is away at war. He's a pretty interesting mix of a guy who is very much his own man."

Ken did a bit of homework as the character developed: "I read a couple of books with descriptions of old aristocrats. Mick Jackson wrote a novel called The underground man which is a fictional account based on the life of a Duke in Nottinghamshire in the late 19th century who was the remaining son of this family that had inherited a huge house. He had built lots of tunnels and was fascinated by science, and he was a wonderful starting point for this character."

Film maker Mick Jackson's Booker-nominated first novel is about the 5th Duke of Portland (1800-1879), a genial but cracked Victorian aristocrat who spent his days conceiving a network of carriage-wide tunnels to run beneath his sprawling Nottinghamshire estate. They took five years and hundreds of labourers to complete.

Ken continues: "I also saw this very charming documentary about Dennis Thatcher who was obviously a bright man who sometimes covered things up with a sort of twinkly mock oafish persona. That was also a bit of an influence as he came across so interestingly."

Ken was aware of the works of E Nesbit although he had never read FIVE CHILDREN AND IT: "I was particularly familiar with the film of THE RAILWAY CHILDREN which is not just an excellent film but also a nostalgic, memory-filled image of Britain at a time when people had jolly good fun and lots of adventures and were kind to each other. There was also a kind of innocence about it; it wasn't soft but filled with the curiosity and desire for adventure in children."

Ken settled down to read first the book and then the script: "I was really impressed at how much work had been done on the screenplay. Firstly it is updated to the First World War which is a legitimate way of introducing a different kind of tension and emotional quality to the story. It seemed to me that David had built on what E Nesbit had done so charmingly with the relationships between the children, with a tone that was happily eccentric and individualistic, unafraid to be quirky.

"E Nesbit makes leaps in the imagination. She happily embraces a surreal quality and was a bit of a pioneer; it's a different kind of comedy from the world of Lewis Carroll. It's very outdoorsy, very adventure-led, very physical, without being so hearty and male that it excludes girls. She somehow managed to create a very particular world in which you could have enormous amounts of fun. On one level you have a really sweet, charming and interesting period yarn, but there is also a rather subversive family drama with great eccentricity and terrific wit when another completely magical element is brought in the shape of our sand-fairy and the voice of Mr Izzard.

"I thought the screenplay had real charm and had made the changes necessary to make it suitable for the big screen. I remember thinking - at the age of 42 perhaps I'm not one to judge and I don't have any kids of my own - but I would have thought this would be a really 'cool' movie. Somehow the action and adventure keep it in a period which retains its unusual character, but it is full of the timeless sense of fun and adventure that all children like to have on their summer holidays. I was very happy to come on board and try and make Uncle Albert memorable."

He continues: "Uncle sets the rules and creates the atmosphere; he invites the children into this rather magical, sometimes foreboding, unusual gothic house, and he also sets the tone of excitement and energy with which they are going to live their summer. At the same time as drawing up his seemingly endless list of rules, he doesn't seem to impose them. He shows the children what it's like to follow a passion, to follow a dream. He's the kind of Uncle you love being cheesed off by; he has these ridiculous rules and he's rather scary because he seems unpredictable, but he's clearly a twinkly, warm-hearted fellow, and often unintentionally funny."

Uncle Albert's appearance reflects what is going on his head: "The costume mixes faintly dandyish qualities with comfort. He's actually rather interested in clothes, and they were probably made beautifully, but they all seem to clash and are now rather threadbare. He's someone who doesn't mind that the waistcoat doesn't remotely go with the shirt or the hat; everything outside is a reflection of all the things that are going on inside his head which are equally contradictory."

Kenneth Branagh also sports a striking, prosthetic balding head for the part: "Uncle Albert has swept-back hair and a large domed head indicating this crazy brain-box. I liked the idea as I haven't done much in prosthetics before. As a character actor you run out of different looks once you've done every version of facial hair. It was time for a change. It took a couple of hours to put on each morning and I could feel myself getting a bit more bustly at every stage of the process. It was funny when I caught myself in the mirror; it says a lot before I even open my mouth."

However filming took place at Shepperton Studios during a long, hot summer heatwave, during which time Ken was also appearing in rep at the National Theatre in a sell-out production of David Mamet's EDMOND: "I obviously couldn't shave my head because I needed my own hair for the play. So I had to wear a bald cap underneath a very tight prosthetic. As you can imagine, it got a little toasty under my prosthetic dome! After two or three days of wearing it I constantly felt as if I were still wearing a phantom crash helmet. I don't normally sweat that much, but I did under all that!"

He adds: "I admit that if I could have had one wish each day until the sun went down, I would have wished that when it was very hot, underneath my prosthetic bald head I had a sort of helicopter cooling device which ran across the top of my noddle and kept me cool until it was time to take it off! That is rather an eccentric wish, but if you'd been under my bald cap, I think you would wish for the same thing. And for world peace, obviously..."

Ken thoroughly enjoyed working with the children as well as with Alex Pownall, who plays his 'mini-me' son: "Alex is very energised and good fun to work with and I instantly felt some kind of natural rapport. He's really good company. Horace is as vivid a character as his father. But their relationship is somewhat complicated. Horace is not without personality issues and he makes himself lonely. He feels slightly rejected by his father who is wrapped up in his many interests and feels that Horace should just get on with it, which means that affection is dolloped out rather arbitrarily. But you see the relationship develop into mutual love and respect without getting gooey - it has a nice blurry edge that makes you feel they might become good mates as they get older. They're certainly a good pair of comic companions."

He continues: "All the children are fantastically impressive with compelling faces and personalities. They are very nice, easy and un-thrown for people with a limited amount of experience of the film-making process which can be tedious unless you are ready to observe. They are fantastic listeners with amazing powers of concentration and are always right in the moment. They keep it very real and natural and the magic and the strangeness of the house are reflected on faces still finding their character.

"They are also incredibly disciplined; they worked long hours in enormous heat and it might have been easy to get scratchy and a bit cranky, but they stayed sharp on their lines and they varied their pace and performance. I am quite certain that the audiences will want to be the children's friend, want to get into the picture and join them on those adventures."

He adds: "FIVE CHILDREN AND IT presents an unusual picture of the Edwardian period but with a contemporary feeling. The children bring an essential, raw, edgy youth up against the formality of Uncle and some of the other characters. You want to be on their side against petty authority. Although the story is very good-hearted, it introduces a bit of the darkness and sense of foreboding which is part of the process of growing up - how you start to worry about what is happening to your parents, in this case your father, for example. People will recognise and vicariously enjoy the way in which the children begin to grow up before our very eyes, and this mingles with the tension and excitement. The stakes are high at various times and I like that."

He concludes: "FIVE CHILDREN AND IT is a story that doesn't feel patronising. David has taken the characters from the book and brings that sense of fun, adventure, danger and magic into the cinema. It succeeds really well on the page and I hope it works here. It's an intriguing and bold title which already has a twinkle in its eye. I like to think that audiences will be surprised at how fresh and contemporary the film feels within a period setting. They will be compelled by the children's performances, the way in which they have brought the characters on the page to life. There's a freshness and an energy to FIVE CHILDREN AND IT; it's everything you'd expect and nothing you'd expect at the same time. And that's probably just the way 'It' would like it to be..."