Late last year Republic raised thousands of pounds to make Take Back the Duchy, a new campaign film.
With the help of a professional documentary maker work on the film is in advanced stages. We've been talking to experts, commentators and Duchy tenants about how the estate gives Prince Charles money, privileges and power.
What's been particularly shocking is how so many local tenants of the Duchy are scared to speak out. They fear losing homes and livelihoods if they go on record criticising the way the Duchy behaves.
The Duchy of Cornwall continues to limit tenants' rights, demand more money from residents and local communities and resist serious scrutiny. Meanwhile around £20m flows from the Duchy into Charles's pockets.
You can find out more about the Duchy of Cornwall and Republic's campaign at www.republic.org.uk/duchy