So they could theoretically drill/destroy/crack the safe in the case of an emergency where codes could not be transmitted. That is why British submarines have

So they could theoretically drill/destroy/crack the safe in the case of an emergency where codes could not be transmitted. That is why British submarines have letters of last resort, to be opened and followed if there are no communications. https://en.wikipedia.org/wiki/Letters_of_last_resort https://en.wikipedia.org/wiki/Letters_of_last_resort