On Tuesday three police officers were seen standing at the spot where a ladder was used for Mr Hatch's ascent. His fellow campaigner Mr Pyke, who dressed as Batman's sidekick Robin, was stopped by armed police at the scene.
Mr Hatch, from Cheltenham in Gloucestershire, was arrested on suspicion of criminal damage.
Mr Pyke, 48, also from Cheltenham, was questioned about aiding and abetting a criminal act.
Following the incident Mr Blunkett argued the Met Police had "acted correctly" in assessing the threat posed by Mr Hatch.
Later he insisted that he was "calm but not complacent" about the intrusion and said there was no reason to demand resignations "for the sake of a 24-hour headline", BBC News reported.
The tabloids scoffed, government ministers vowed to step up security and Britons had a good laugh -- that is when they weren't worrying about the security implications.