Milligan is his surname. Spike is his nickname, what else could it possibly be.
Spike was a submariner, but not on this sub.
A tour guide who had lived the life of what he was talking about is vastly more interesting than one who has read a book about it.
I would say from listening to Spike that life on a sub was tough, very tough.
Also very interesting and challenging. You had to be skilled to work on a sub, very good in the classroom as well as manual skills.