Back when my night in central London was ridiculously popular, I used to employ a mate of mine to help out on the night. He was generally the front of house person, dealing with the queues, but part of his job was to come and check if I needed a drink, and on one occasion he stepped in and DJ-ed when I had to go and deal with a situation that required an ambulance. I guess he could have been described as a DJ assistant, but really he was the fixer of the night, the Harvey Keitel who kept everything running smoothly. For a while there, I couldn't have survived without him.