The process was very straightforward. My wife had done her research on the requirements and the process to follow for the London Embassy through visajourney posts and was well aware of what she had to do. She followed the basic steps of ensuring no electronics in the building, getting there on time, etc etc.
Once she was in, don't know how long it took for her to be called, however, going by the timings of the txt message I had from her right before she dropped her phone at the shop across the street, till the time she called me to say it was approved was in total 2.5 hours.
Interview questions were straightforward:
1. Are you born and brought up in the UK
2. When and how did you meet
3. Did you have indian wedding as well? was it a big one?
4. Why are you going to US?