In 1959, at the age of eighteen, Wiseman became the youngest person ever to pass selection for the SAS, joining from the Parachute Regiment, which he had joined a year earlier. He went on to serve in the SAS for 26 years, rising to the rank of Warrant Officer. Wiseman was also Head of Operational Research 22 SAS, set up a counter hijack team known as SP Team and founded the SAS Counter-Terrorist Team (who are well known for their involvement in the Iranian Embassy siege )