Chattan’s position is the correct one. Detachment 2702 has a very clear and specialized mission which most certainly does not include opening safes from U-boats. For that matter, it does not include going onto abandoned U-boats to recover safes, or other crypto data, in the first place. The only reason they did that was because they happened to be the only people with Ultra clearance who were in the neighborhood, and U-553’s precarious position did not give Bletchley Park time to send out its own experts.