I think crew only require the Crewmans Visa, which I believe is the C1 . The other (D1) is a normal tourist visa, done at the same time as a courtesy to crew. As for the hassle of travelling to the US Embassy, I do wonder what some pprune posters would suggest as an alternative?
A posters question "Another thing - why should British passport holders be subjected to 3 hours plus queueing to get through US immigration??? " Probably because , the average Brit doesn't have the correct pasport, or on the case of some of the pax on my flight (and unfortunately ahead of me in the immigration queue), don't know their left finger from their right finger, causing the computer system to lock up for 10 mins while the Immigration Officer rebooted his Windows driven computer.
IMHO, the USA does perceive a potential terrorist threat from the UK , perhaps as a result of our safe haven immigration policies?. As a result, some of us are forced to jump through these frustrating hoops. BTW, a lot of crew avoided all this on BA advice and renewed their visas early. This meant avoiding the need to pop up to central London "for a chat". It was widely promulgated at the time in the various company publications.
What I think is a shame, are the people who given any problem or hardship will take the opportunity to take it out on the pax or the company.