It has become a classic of children’s literature, as well as being widely read as an historical novel, and has been continuously in print since its first publication. Indeed, Rosemary Sutcliff – my godmother and, to be precise, first-cousin-once-removed – said often that she wrote for children aged ‘eight to 88’. The Eagle of the Ninth has sold over a million copies English alone, and been translated into 25 languages.

Astonishingly, Rosemary wrote the book early in her career as a published author, which began in 1950. In 1955, after the death of my father– he was a close friend of hers, sharing upbringings as only children – my mother, myself aged about 2½, and my sister of 6 months moved to live in West Sussex, close to Rosemary, and so I grew up with ‘Romie’, as I knew her, as an integral part of my life. She stayed with us over Easter and Christmas most years, and we visited her often at her home at Swallowshaw in West Sussex, a house made on one floor from the outhouses of a local landowner’s mansion, arranged Roman-villa-like around little courtyards and long corridors.

Now that I find myself being asked about her, her writing, The Eagle of the Ninth in particular, and ‘What she would have thought of the film The Eagle’, I am reminded that often, since her death in 1992, I have wished I had paid more attention to conversations over meals and in her study. And as I craft this post, I find myself wishing, also, that she had passed even a few of the writing genes to this family member. But I was a boyish teenager more interested in cricket, rugby and guitar-playing than the intricacies of writing historical novels, her approach to research, and her take on storytelling.

In later life I did come to talk with her more about writing, and her love of stories in many genres. So it is that I presume to think she would have been delighted that The Eagle of the Ninth has been transformed into a film. She was a storyteller at heart, and loved stories told on film and TV as well as read aloud and on stage. She loved the BBC’s Children’s Hour radio rendition of the book in 1957. She adored the BBC TV version in 1974, loving in particular Marcus, as played by Anthony Higgins. In fact, she had a soft spot for that actor. As she did for Marcus, who she described as a favourite hero and someone she had been in love with all her life. And she would, I believe, have loved the star of The Eagle, Channing Tatum.

But when I first learned that Channing Tatum had been cast as Marcus, I demonstrated how out of touch I was by speaking of him for six months as Tatum Channing. Once I finally had his name straight, and caught up with films such as Step Up and Dear John, I learned that his casting surprised many industry observers: he has as tenacious a band of critics as he has devoted fans.

Having now seen the film three times, I think his casting was clever: he is a strong, determined, intelligent, moral, wounded but, yes, good looking, presence, and entirely believable as the son who seeks to restore a father’s reputation, which was in tatters because as commander of the ninth legion he lost the eagle (the standard) and all his men. There could be no greater shame and dishonour for a commander of fighting men in Rome.

Also controversial, at least for devotees of the book, may be the alterations to Rosemary’s story. To all who have asked my opinion, I have ventured simply that Rosemary admired great storytelling. She surely understood that different media imposed different requirements, and she would have been sensitive to how readers and filmgoers are creatures of the times they live in. She moved from describing the world in small miniature paintings (she trained at Bideford Art College, exhibited nationally and was a Fellow of the Royal Society of Miniaturists) to what she called ‘the bigger canvas’ of novels. She helped adapt her Song for a Dark Queen for the stage. And she created community plays for Chichester Festival Theatre.

I believe she would have respected the choices that director Kevin Macdonald, producer Duncan Kenworthy and writer Jeremy Brock made in pursuit of a persuasive, exciting adventure story on film. She would perhaps also have been delighted that Macdonald’s vision was in part of a Western, a genre that Rosemary loved. I recall many evenings when we sat watching Westerns on TV or video in her sitting room next to her study.

She may, too, have appreciated Macdonald’s use of the context of current (US) imperial wars. She would have loved the celebration of the Scottish landscape. She would not have welcomed, however, the film studio’s decision to shorten the title to The Eagle, in the English version at least. And she may have regretted that the film does not show some of the nuances of the relationship between Marcus and his slave, Esca.

The Eagle of the Ninth in book and film is an exciting quest story, as well as a tale of male-friendship. But, for those who wish to see more, there are themes of the insider and the outsider, the individual and the group, as well as honour, trust and loyalty to family and ‘tribe’. If the film creates more readers for the book and Rosemary’s other novels she would, of course, have been delighted – as indeed will all those publishers, agents and family who have a financial interest in, as well as a passion for, her writing.

In 1980, The Times lauded Rosemary as one of the top 20 writers in English of the century. When she died in 1992, the Guardian obituary called her ‘an historical writer of genius’ as well – correctly – as ‘impish and irreverent’. All her writing life, her books excited and inspired people who became historians and archaeologists, as well as writers and storytellers.

I am delighted she has so inspired film-makers of the talents and reputation of those who have made The Eagle, and that they have so lovingly recreated the world she re-imagined. True, the film has received mixed reviews in the US. But I choose to go with my reading of them.

Thus, with Time Out New York I believe, ‘You’ll gladly enslave yourself to Kevin Macdonald’s rollicking sword-and-sandal epic … … a beautifully executed piece of pulp fiction’, even if it is not so much epic as adventure story, and the novel is certainly not pulp fiction. I hope you will enjoy what New York Magazine, called an ‘unfashionably exciting adaptation’, and what Roger Ebert called a ‘rip-snorting adventure tale’.  But, most importantly, I hope the film drives new readers to enjoy the The Eagle of the Ninth.