Maximum retirement age for a colonel?

A question about : Maximum retirement age for a colonel?

I know it's not the right forum but please bear with me.

I am writing a book, with a retired SAS Lt. Colonel as one the the characters. He joined young and remained in until he retired. I've googled but can't get a straight answer. It seems to be 20 - 22 years for a rating and 30 years for officers?

TIA

Best answers:

• No one knows? Wow!
• Age 55 is when you get the "full service pension" and is the current compulsory retirement age I believe it is rising to 60 with the pension changes.
  Service beyond that is possible at the discretion of the service eg if you have specialist skills they want to keep but could be via the reserves rather than regulars
• My bad. I am also including the SBS so got mixed up.
  Thanks.
• Thanks for that. I've learned more here than from Google. Go figure.