That depends, Danny.
It could either be MRES Missing Research and Enquiry Service or MREU, last word being Unit. They often used ex aircrew or, as in the case of P/O Hubert Brooks of No. 419 Sqn. former POWs.
Brooks, as a F/Lt, was in charge of the Scandinavian section. This after three escapes and two years fighting with the Polish Home Army. He was also RCAF and I have seen RNZAF, RAAF, RCAF and RAF members as staff in MREUs. "Missing Believed Killed" by Stuart Hadaway is the go-to book on the topic.
So, any idea which service Clowes was a member of?
Edited to add: Another problem with IDing are wrong initials. In the excerpt from the MREU report in this
loss, we have an S/Ldr ACW Clowes signing the report for the OC No. 2 MREU. I looked at the physical file at NAA. No helpful numbers.
Regards,
Dave