Originally self-published by Roderick Gordon and Brian Williams as The Highfield Mole in March 2005, the book came to the attention of Barry Cunningham of The Chicken House, who signed the authors for the first two books in the series. With the new title Tunnels, it was released in the UK on 2nd July 2007, and rights were sold to 35 publishers throughout the world. Negotiations are underway with Relativity Media in the US for a film to be made.