Relativity Media has acquired film rights to Tunnels, the first in a proposed children's franchise by first-time British authors Roderick Gordon and Brian Williams.

Company chief Ryan Kavanaugh will produce with Mark Canton, currently riding high on the global success of 300. Danny Davids and Neil Canton will serve as executive producers.

Tunnels will arrive in UK shops this summer and the US in January 2008 through Chicken House/Scholastic.

It has already generated advances of more than $1m and pre-publication rights in more than 21 languages, and the authors have already completed a sequel and are working on a third volume.

The story centres on a 14-year-old London boy with a passion for digging who investigates the tunnel that his father disappeared into and discovers a terrifying secret.

'Tunnels represents the kind of timeless literary phenomenon that does not come around very often,' Kavanaugh said. 'The book has already generated such a huge response across the world and we look forward to putting the enchantment that Gordon and Williams first brought to the page, to the screen.'

'The originality of the book and its sequels, which uniquely combine the adventure of Indiana Jones with the magic of Narnia, along with its franchise potential, is what attracted Ryan and myself to Tunnels,' Canton added.

Canton is represented by Jake Bloom and Ralph Brescia of Bloom Hergott Diemer Rosenthal and LaViolett.

Gordon and Williams are represented by Chicken House Entertainment with Stephen Moore at the Paul Kohner Agency.