When I used to manage major concerts and events, some owners were hesitant to hire because they could not familiarize themselves with a work force in an interview or consultation, and liked more time to become familiar with my crew.
When you are in control of an event at your venue, you need to have the proper events staff London available to work for you. A work force who is not familiar with entertainment events may not be able to properly lead a fan out of a venue in the case of emergency or control a crowd if it gets out of hand. Whenever something bad happened at an event I was managing, it come back on me if my crew could not properly contain it.
Sometimes, it is best to contract with a third party to get the most qualified staff at your venue. You can find the best by searching online.