Why would his signature be clearly visible as Guido if his name was Guy?
If it quacks like a duck .
I just watched a video about it. All sorts of red flags. Like they claimed they built a tunnel to Parliament, but then that wasn't true. Forged documents, confessions under torture, spies .... way way way too much intrigue.
This is almost certainly a distorted historical event for which we will probably never know what really happened.