I have lived near Broadmoor all my life and there have only been a few escapes. Was very annoying when we were kids as we were not allowed out to play and it took ages to get anywhere. Now I have dc I can fully understand it and why my DM slept with a hammer under her pillow!
I have several friends working in mental health and forensics is a hard slog. When I worked as a RMN none of the patients ever plotted together to escape, maybe too wrapped up in their own illness.