You might want to look into the story of Lionel Crabb, an SAS frogman suspected of being killed while performing espionage against a soviet warship.

https://en.wikipedia.org/wiki/Lionel_Crabb

That's an interesting read.

I wonder if the DNA is in good enough shape to tell us whether or not the body is his.

Probably more relevant to look at the UK SBS rather than the SAS.

Where did you get the SAS part from?

Special Force: The Untold Story of 22nd Special Air Service Regiment (SAS)

https://books.google.co.uk/books?id=CJ73AgAAQBAJ&pg=PA289&lp...

That doesn't say that he was in the SAS. It just has his name and SAS in the same paragraph.

It says that in the past MI6 needed a person with military skills do something, as was the case with Crabb, so they decided to start cross-training SAS people to do that in the future.

Neither the Wikipedia article nor this endnote says that Crabb was SAS.

I was just hazarding a guess at the question: "Where did you get the SAS part from?"