Original sentence: However, it is curious to know that there has been several very serious investigations about the Englandspiel.Many agents who were caught and forced to continue their broadcasting sent, in their messages, hidden codes which said they had been compromised.These were ignored
Edited sentence: Further, it was noticed.However, there have been several very serious investigations about the Englandspiel.Many agents who were caught and forced to continue their broadcasting.Their messages contained hidden codes that showed they had been compromised.These were ignored by the SOE