Beaumont, who has been at the charity for ten years, is leaving at the end of the year to produce a sci-fi thriller.
The charity's comms stalwart wrote a script, which his production company Little Dude Films turned into a 15-minute demonstration film. It attracted interest and a full-length version is to be developed by a consortium of British, US and Canadian backers.
Beaumont was director of comms between 2001 and 2007, and then took the role of campaigns director with a focus on public affairs. He will still be involved in the PR industry through his consultancy Edge PR.
Looking back on his role at the charity, he said: 'It's been amazing; the most important thing I will ever do.'
Beaumont is to be replaced by Nick Bason, who has joined from being policy and public affairs manager at Employers' Forum on Disability. Bason has already started his new role, in order to handle the party conference season.
Bason has also worked as a policy adviser for the Association of British Insurers and a ballot adviser for the Electoral Reform Services.
Beaumont's film, called Deathless, is a time-travelling detective story about a man who goes back in time to save the life of his wife.
He explained that he was inspired to write the film as 'escapism' over the past few years.